JP2019086469A - Radar device and arrival direction estimating device - Google Patents

Abstract

To suppress an increase in computation amount and measure an angle with high accuracy.SOLUTION: In a direction estimation unit 214, a horizontal direction array maximum likelihood estimation unit 242 calculates, using the received signal of a first virtual liner array, a first maximum likelihood value that corresponds to NW angles in a first direction by a maximum likelihood estimation process for the first direction, and extracts a first arrival angle candidate of arrival wave in the first direction that includes at least the first maximum likelihood value. A vertical direction array maximum likelihood estimation unit 243 calculates, using the received signal of a second virtual liner array, a second maximum likelihood value that corresponds to NW angles in a second direction by a maximum likelihood estimation process for the second direction, and extracts a second arrival angle candidate of arrival wave in the second direction that includes at least the second maximum likelihood value. A horizontal/vertical direction array maximum likelihood estimation unit 244 estimates, using the first arrival angle candidate and the second arrival angle candidate, the arrival angle of NW arrival waves in a two-dimensional plane that extends in the first and the second directions.SELECTED DRAWING: Figure 6

Description

  The present disclosure relates to a radar device and an arrival direction estimation device.

  In recent years, studies on a radar apparatus using a radar transmission signal with a short wavelength including microwaves or millimeter waves capable of obtaining high resolution have been advanced. Further, in order to improve the safety outside, development of a radar apparatus (wide-angle radar apparatus) for detecting an object (target) including a pedestrian in a wide-angle range is also required besides vehicles.

  For example, a pulse radar device that repeatedly transmits pulse waves is known as a radar device. The reception signal of the wide-angle pulse radar that detects a vehicle / pedestrian in the wide-angle range is a mixture of multiple reflected waves from a target (for example, a vehicle) present at a short distance and a target (for example a pedestrian) present at a long distance It becomes a signal that has been For this reason, (1) the radar transmitter needs to be configured to transmit a pulse wave or a pulse modulated wave having an autocorrelation characteristic (hereinafter referred to as a low range side lobe characteristic) which results in a low range side lobe, (2) In the radar receiver, a configuration having a wide reception dynamic range is required.

  The following two configurations can be mentioned as the configuration of the wide-angle radar device.

  First, the pulse wave or the modulation wave is mechanically or electronically scanned by using a directional beam with a narrow angle (a beam width of several degrees) to transmit a radar wave, and the directional beam with a narrow angle is transmitted. Is used to receive the reflected wave. In this configuration, a large number of scans are required to obtain high resolution, so the ability to follow targets moving at high speed is degraded.

  The second is that the reflected wave is received by an array antenna composed of a plurality of antennas (antenna elements), and the angle of arrival of the reflected wave (arrival direction) by a signal processing algorithm based on the reception phase difference with respect to the element spacing It is the composition using a method (Direction of Arrival (DOA) estimation) of estimating. In this configuration, even if the scan interval of the transmit beam in the transmit branch is thinned out, the arrival angle can be estimated in the receive branch, so the scan time can be shortened and the followability can be improved compared to the first configuration. Do.

  For example, as a direction of arrival estimation method, a Fourier beam former method capable of obtaining an angular resolution similar to that of the array antenna beam width or a high resolution method capable of realizing an angular resolution narrower than the antenna beam width has been proposed.

  There is a maximum likelihood estimation method as one of high resolution methods (see, for example, Non-Patent Document 1). In the direction of arrival estimation method using the maximum likelihood estimation method, an evaluation function derived based on the principle of maximum likelihood estimation is minimum or maximum in a search grid defined within an arrival angle area where arrival of an arrival wave is assumed. It is a method of searching for the arrival wave angle (maximum likelihood value) which becomes The number of incoming waves is included as a parameter in this evaluation function.

  The maximum likelihood estimation method is applicable to the direction of arrival estimation method regardless of the shape of the array antenna, and is high even when there is a high correlation between received signals of a plurality of incoming waves (coherent waves) It is possible to separate incoming waves with accuracy.

JP 2008-96137 A

Ilan Ziskind and Mati Wax, "Maximum Likelihood Localization of Multiple Sources by Alternating Projection," IEEE Trans. On Acoustics, Speech, and Signal Processing, Vol. 36, No. 10, Oct. 1988 J. Li, P. Stoica, "MIMO Radar with Colocated Antennas," Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007 J. A. Fessler and A. O. Hero, "Space-altering generalized expectation-maximization algorithm," IEEE Trans. Signal Process., Vol. 42, no. 10, pp. 2664-2677, Oct. 1994.

  However, while the direction of arrival estimation using the maximum likelihood estimation method can obtain excellent angle measurement performance, it is necessary to make the search grid finer in order to estimate the arrival angle (direction of arrival) with high accuracy. The amount of computation may increase.

  One aspect of the present disclosure provides a radar device and an arrival direction estimation device capable of performing angle measurement with high accuracy while suppressing an increase in calculation amount.

  A radar device according to an aspect of the present disclosure includes a transmitting unit that transmits a radar signal using a transmitting array antenna, and a receiving unit that receives a reflected wave signal in which the radar signal is reflected at a target using a receiving array antenna. And a direction estimation unit that estimates an arrival angle of the received reflected wave signal, and the direction estimation unit is virtually configured based on the arrangement of the transmission array antenna and the reception array antenna. Among the plurality of virtual reception antennas included in the reception array, the reception signal of the first virtual linear array configured by the virtual reception antennas linearly arranged in the first direction is used for the first direction. A maximum likelihood estimation process calculates a first maximum likelihood value corresponding to NW (NW is an integer of 1 or more) angles in the first direction, and includes at least the first maximum likelihood value. A first estimation unit that extracts a first arrival angle candidate of an incoming wave in the first direction, and a linear direction in a second direction orthogonal to the first direction among the plurality of virtual reception antennas A second corresponding to the NW angles in the second direction by maximum likelihood estimation processing with respect to the second direction using a reception signal of a second virtual linear array configured by the virtual reception antennas arranged. A second estimation unit that calculates a maximum likelihood value of the first arrival angle candidate and extracts a second arrival angle candidate of the arrival wave in the second direction including at least the second maximum likelihood value; And a third estimation unit configured to estimate angles of arrival of the NW arrival waves in a two-dimensional plane extending in the first direction and the second direction, using the second arrival angle candidate. Do.

  An arrival direction estimation apparatus according to an aspect of the present disclosure is an arrival direction estimation apparatus that estimates an arrival angle of a received signal using a plurality of reception antennas, the first among the plurality of reception antennas. NW (NW is 1 or more in the first direction) by the maximum likelihood estimation processing for the first direction using the reception signal of the first linear array configured by the receiving antennas linearly arranged in the direction Calculating a first maximum likelihood value corresponding to an integer number of angles, and extracting a first arrival angle candidate of an incoming wave in the first direction including at least the first maximum likelihood value A second linear array of received signals comprising a second linear array of receiving antennas arranged in a second direction orthogonal to the first direction among the plurality of receiving antennas; Maximum likelihood estimation process for the two directions A second maximum likelihood value corresponding to the NW angles in the second direction, and a second arrival angle candidate of the arrival wave in the second direction including at least the second maximum likelihood value; By using the second estimation unit for extracting the second arrival angle candidate and the first arrival angle candidate, the NW in the two-dimensional plane extending in the first direction and the second direction. And a third estimation unit configured to estimate an arrival angle of an incoming wave.

  Note that these general or specific aspects may be realized by a system, method, integrated circuit, computer program, or recording medium, and any of the system, apparatus, method, integrated circuit, computer program, and recording medium It may be realized by any combination.

  According to one aspect of the present disclosure, angle measurement can be performed with high accuracy while suppressing an increase in the amount of computation.

  Further advantages and effects of one aspect of the present disclosure are apparent from the specification and the drawings. Such advantages and / or effects may be provided by some embodiments and features described in the specification and drawings, respectively, but need to be all provided to obtain one or more identical features. There is no.

Diagram showing arrangement example of transmitting and receiving antennas Diagram showing arrangement example of virtual reception array Block diagram showing the configuration of a radar apparatus according to one embodiment A diagram showing an example of a radar transmission signal according to an embodiment Block diagram showing another configuration of the radar transmission signal generation unit according to one embodiment The figure which shows an example of transmission timing of the radar transmission signal concerning one embodiment, and a measurement range Block diagram showing an internal configuration of a direction estimation unit according to an embodiment The figure which shows the example of arrangement of the transmitting and receiving antenna concerning one embodiment A diagram showing an arrangement example of a virtual reception array according to an embodiment A diagram showing an example of a search grid during two-dimensional maximum likelihood estimation according to an embodiment The figure which shows an example of the number of times of search to the number of search grids concerning one embodiment The figure which shows an example of the reduction ratio of the frequency | count of a search with respect to the number of search grids which concerns on one Embodiment Block diagram showing an internal configuration of a direction estimation unit according to Variation 1 of an embodiment Block diagram showing an internal configuration of a direction estimation unit according to variation 2 of one embodiment Block diagram showing an internal configuration of a direction estimation unit according to variation 2 of one embodiment A diagram showing an example of arrangement of transmitting and receiving antennas according to Variation 3 of one embodiment A diagram showing an example of arrangement of virtual reception arrays according to variation 3 of one embodiment

  As a radar device, in addition to the receiving branch, a configuration (sometimes referred to as a MIMO radar) for performing beam scanning by signal processing using a transmitting / receiving array antenna is also proposed, including a plurality of antennas (array antennas) in the transmitting branch. (See, for example, Non-Patent Document 2).

  In the MIMO radar, a virtual reception array antenna (hereinafter referred to as a virtual reception array) equal to the product of the number of transmission antenna elements and the number of reception antenna elements at the maximum is realized by devising the arrangement of antenna elements in the transmission / reception array antenna. It can be configured. As a result, the effect of increasing the effective aperture length of the array antenna can be obtained with a small number of elements, and the angular resolution can be improved.

  By performing the arrival direction estimation process using the reception signal of such a virtual reception array, it is possible to perform an angle measurement with an increased resolution.

  In addition to the vertical or horizontal one-dimensional scanning (angle measurement), the MIMO radar is also applicable to beam scanning on a two-dimensional plane extending in the vertical and horizontal directions.

As an example, FIG. 1A shows a transmit array antenna including four transmit antennas (Tx # 1 to Tx # 4) vertically arranged, and four receive antennas (Rx # 1 horizontally arranged). 7 shows a receive array antenna comprising. In FIG. 1A, the transmitting antennas are arranged at equal intervals (d _v ) in the vertical direction, and the receiving antennas are arranged at equal intervals (d _H ) in the horizontal direction.

FIG. 1B shows a virtual receive array including the transmit and receive array antennas of the antenna arrangement shown in FIG. 1A. The virtual reception array shown in FIG. 1B includes 16 elements of virtual reception antennas (VA # 1 to VA # 16) in which four antennas in the horizontal direction and four antennas in the vertical direction are arranged in a rectangular shape. In FIG. 1B, the horizontal and vertical element intervals of the virtual reception array are d _H and d _V , respectively. That is, the horizontal and vertical aperture lengths D _H and D _V of the virtual reception array are 3 d _H and 3 d _V , respectively.

  In such a virtual reception array, when applying the DOA estimation method using the maximum likelihood estimation method, the DOA angle with which the evaluation function is minimized or maximized in the search grid defined in the vertical direction and the horizontal direction is searched Do. At this time, as the search grid is made finer in order to estimate the arrival angle with high accuracy, the amount of calculation for the search increases.

  On the other hand, there is known a method of utilizing local search when estimating the arrival angle with high accuracy (for example, the Alternative Maximization method described in Non-Patent Document 1). However, such a method may lead to a local solution if the initial value is not set properly, which may significantly deteriorate the angle measurement accuracy.

  Further, according to Patent Document 1, in the arrival angle area where arrival of an arrival wave is assumed, the search grid is set relatively coarsely to perform the initial search, and the search range is partially limited after the initial search. A method is disclosed that reduces the amount of computation by making the range grid finer in stages.

For example, in the case of estimating the arrival angles of K arrival waves in two dimensions in the vertical direction (elevation) and horizontal direction (azimuth) using the maximum likelihood estimation method, from the (NGV × NGH) two-dimensional grid, In order to search K different combinations, the number of searches N _search is expressed as in the following equation (1). Note that NGV represents the number of search grids in the vertical direction, and NGH represents the number of search grids in the horizontal direction.
N _search = _{(NGV × NGH)} C _K (1)

  In equation (1), for example, when the number of search grids in the vertical direction NGV = 10, the number of search grids in the horizontal direction NGH = 10 and the number of incoming waves K = 2 as the initial search grid, 4950 times (= 100 A search of × 99/2) is required.

  Therefore, in the method disclosed in Patent Document 1, the amount of operation for searching increases. Further, in Patent Document 1, when the number of search grids is reduced to reduce the amount of calculation, the angle measurement accuracy is degraded.

  Therefore, in one aspect according to the present disclosure, a method of reducing the number of searches (operation amount) while maintaining the angle measurement accuracy in angle measurement processing when the direction of arrival is estimated using the maximum likelihood estimation method will be described.

  Hereinafter, embodiments according to an aspect of the present disclosure will be described in detail with reference to the drawings. In the embodiments, the same components are denoted by the same reference numerals, and the description thereof will be omitted.

  In the following, in the radar device, a configuration will be described in which different transmission signals code division multiplexed are transmitted from a plurality of transmission antennas in a transmission branch, and each transmission signal is separated and reception processing is performed in a reception branch. However, the configuration of the radar apparatus is not limited to this, and different transmission signals frequency division multiplexed are transmitted from a plurality of transmission antennas in the transmission branch, and each transmission signal is separated and reception processing is performed in the reception branch. It may be a configuration. Also, similarly, the configuration of the radar apparatus may be a configuration in which a transmission branch transmits a time division multiplexed transmission signal from a plurality of transmission antennas, and a reception branch performs reception processing.

[Configuration of radar device]
FIG. 2 is a block diagram showing the configuration of the radar device 10 according to the present embodiment.

  The radar device 10 includes a radar transmission unit (transmission branch) 100, a radar reception unit (reception branch) 200, and a reference signal generation unit 300.

  The radar transmitter 100 generates a radar signal (radar transmission signal) of high frequency (radio frequency) based on the reference signal received from the reference signal generator 300. Then, the radar transmission unit 100 transmits a radar transmission signal at a predetermined transmission cycle using a transmission array antenna configured of a plurality of transmission antennas 106-1 to 106-Nt.

  The radar receiver 200 receives a reflected wave signal, which is a radar transmission signal reflected by a target (not shown), using a reception array antenna including a plurality of reception antennas 202-1 to 202-Na. The radar reception unit 200 performs processing in synchronization with the radar transmission unit 100 by performing the following processing operation using the reference signal received from the reference signal generation unit 300. That is, the radar receiver 200 performs signal processing on the reflected wave signal received by each receiving antenna 202, and at least detects the presence / absence of a target and estimates the direction. The target is an object to be detected by the radar device 10, and includes, for example, a vehicle (including four wheels and two wheels) or a person.

  The reference signal generation unit 300 is connected to each of the radar transmission unit 100 and the radar reception unit 200. The reference signal generation unit 300 supplies a reference signal as a reference signal to the radar transmission unit 100 and the radar reception unit 200, and synchronizes the processing of the radar transmission unit 100 and the radar reception unit 200.

[Configuration of Radar Transmission Unit 100]
The radar transmission unit 100 includes radar transmission signal generation units 101-1 to 101-Nt, transmission radio units 105-1 to 105-Nt, and transmission antennas 106-1 to 106-Nt. That is, the radar transmission unit 100 has Nt transmission antennas 106, and each transmission antenna 106 is connected to the individual radar transmission signal generation unit 101 and the transmission radio unit 105.

The radar transmission signal generation unit 101 generates a timing transmission clock by multiplying the reference signal received from the reference signal generation unit 300 by a predetermined number, and generates a radar transmission signal based on the generated timing clock. Then, the radar transmission signal generation unit 101 repeatedly outputs a radar transmission signal at a predetermined radar transmission cycle (Tr). The radar transmission signal is represented by r _z (k, M) = I _z (k, M) + j Q _z (k, M). Here, z represents a number corresponding to each transmitting antenna 106, and z = 1,..., Nt. Also, j represents an imaginary unit, k represents a discrete time, and M represents an ordinal number of a radar transmission period.

  Each radar transmission signal generation unit 101 includes a code generation unit 102, a modulation unit 103, and an LPF (Low Pass Filter) 104. Hereinafter, each component in the radar transmission signal generation unit 101-z corresponding to the z-th (z = 1,..., Nt) transmission antenna 106 will be described.

Specifically, the code generation unit 102 generates the code a (z) _n (n = 1,..., L) (pulse code) of the code sequence of the code length L for each radar transmission cycle Tr. For the codes a (z) _n (z = 1,..., Nt) generated by the respective code generation units 102-1 to 102-Nt, codes having low correlation or no correlation with each other are used. As a code sequence, for example, Walsh-Hadamard code, M-sequence code, Gold code and the like can be mentioned.

The modulation unit 103 performs pulse modulation (amplitude modulation, amplitude shift keying (ASK), pulse shift keying), or phase modulation (phase shift keying) on the code a (z) _n received from the code generation unit 102 to generate a modulation signal. Is output to the LPF 104.

  The LPF 104 outputs, to the transmission radio unit 105, a signal component below the predetermined limited band in the modulation signal received from the modulation unit 103 as a baseband radar transmission signal.

  The z-th (z = 1,..., Nt) transmission radio unit 105 performs frequency conversion on the baseband radar transmission signal output from the z-th radar transmission signal generation unit 101 to obtain the carrier frequency ( Radio frequency (RF) band radar transmission signals are generated, amplified to a predetermined transmission power P [dB] by a transmission amplifier, and output to the z-th transmission antenna 106.

  The z-th (z = 1,..., Nt) transmission antenna 106 radiates the radar transmission signal output from the z-th transmission radio unit 105 into space.

FIG. 3 shows a radar transmission signal transmitted from Nt transmission antennas 106 of the radar transmission unit 100. The code transmission interval Tw includes a pulse code sequence of code length L. A pulse code sequence is transmitted during the code transmission period Tw in each radar transmission period Tr, and the remaining period (Tr-Tw) is a non-signal period. By performing pulse modulation using No samples per one pulse code (a (z) _n ), Nr (= No × L) samples of signals in each code transmission section Tw Is included. That is, the sampling rate in the modulator 103 is (No × L) / Tw. Also, the no signal section (Tr-Tw) includes Nu samples.

  The radar transmission unit 100 may include a radar transmission signal generation unit 101 a shown in FIG. 4 instead of the radar transmission signal generation unit 101. The radar transmission signal generation unit 101a does not have the code generation unit 102, the modulation unit 103, and the LPF 104 shown in FIG. 2, but includes a code storage unit 111 and a DA conversion unit 112 instead. The code storage unit 111 stores in advance the code sequence generated in the code generation unit 102 (FIG. 2), and cyclically reads out the stored code sequence. The DA conversion unit 112 converts the code sequence (digital signal) output from the code storage unit 111 into an analog signal.

[Configuration of Radar Reception Unit 200]
In FIG. 2, the radar receiving unit 200 includes Na receiving antennas 202 to configure an array antenna. The radar receiver 200 further includes Na antenna system processors 201-1 to 201-Na and a direction estimation unit 214 (arrival direction estimation device).

  Each receiving antenna 202 receives a reflected wave signal which is a radar transmission signal reflected to a target (object), and outputs the received reflected wave signal to the corresponding antenna system processing unit 201 as a received signal.

  Each antenna system processing unit 201 includes a reception radio unit 203 and a signal processing unit 207.

  The reception radio unit 203 has an amplification unit 204, a frequency converter 205, and a quadrature detector 206. The reception radio unit 203 generates a timing clock obtained by multiplying the reference signal received from the reference signal generation unit 300 by a predetermined number, and operates based on the generated timing clock. Specifically, the amplifier 204 amplifies the reception signal received from the reception antenna 202 to a predetermined level, the frequency converter 205 converts the frequency of the reception signal in the high frequency band to a baseband band, and the quadrature detector 206 The received signal in band band is converted to the received signal in baseband band including I signal and Q signal.

  The signal processing unit 207 includes AD conversion units 208 and 209 and separation units 210-1 to 210-Nt.

  The I signal is input to the AD conversion unit 208 from the quadrature detector 206, and the Q signal is input to the AD conversion unit 209 from the quadrature detector 206. The AD conversion unit 208 converts the I signal into digital data by performing sampling in discrete time on the baseband signal including the I signal. The AD conversion unit 209 converts the Q signal into digital data by performing sampling in discrete time on the baseband signal including the Q signal.

  Here, in the sampling of the AD conversion units 208 and 209, Ns discrete samples are performed per time Tp (= Tw / L) of one sub-pulse in the radar transmission signal. That is, the number of oversamples per sub pulse is Ns.

  In the following description, using the I signal Ir (k, M) and the Q signal Qr (k, M), the discrete time of the Mth radar transmission period Tr [M] as the output of the AD conversion units 208 and 209 The baseband received signal at k is represented as a complex signal x (k, M) = Ir (k, M) + jQr (k, M). Also, in the following, with respect to the discrete time k, the timing at which the radar transmission period (Tr) starts is set as the reference (k = 1), and the signal processing unit 207 determines k as sample points before the radar transmission period Tr ends. = (Nr + Nu) Ns / No operate periodically. That is, k = 1,..., (Nr + Nu) Ns / No. Here, j is an imaginary unit.

  The signal processing unit 207 includes Nt separation units 210 equal in number to the number of transmission antennas 106. Each separation unit 210 includes a correlation calculation unit 211, an addition unit 212, and a Doppler frequency analysis unit 213. The configuration of the z-th (z = 1,..., Nt) separating unit 210 will be described below.

The correlation operation unit 211 receives discrete sample values x (k, M) including discrete sample values Ir (k, M) and Qr (k, M) received from the AD conversion units 208 and 209 for each radar transmission period Tr, The radar transmitter 100 performs correlation calculation with the pulse code a (z) _n (where z = 1,..., Nt, n = 1,..., L) of the code length L transmitted. For example, the correlation operation unit 211 performs a sliding correlation operation between the discrete sample values x (k, M) and the pulse code a (z) _n . For example, the correlation operation value AC _(z) (k, M) of the sliding correlation operation at the discrete time k in the Mth radar transmission period Tr [M] is calculated based on the following equation.

  In the above equation, the asterisk (*) represents a complex conjugate operator.

  The correlation operation unit 211 performs the correlation operation over the period of k = 1,..., (Nr + Nu) Ns / No, for example, according to the equation (2).

  The correlation operation unit 211 is not limited to the case where the correlation operation is performed on k = 1,..., (Nr + Nu) Ns / No, and measurement is performed according to the existing range of the target to be measured by the radar device 10 The range (ie, the range of k) may be limited. Thereby, in the radar device 10, it is possible to reduce the amount of calculation processing of the correlation calculation unit 211. For example, the correlation operation unit 211 may limit the measurement range to k = Ns (L + 1),..., (Nr + Nu) Ns / No-NsL. In this case, as shown in FIG. 5, the radar device 10 does not perform measurement in the time interval corresponding to the code transmission interval Tw.

  Thus, even when the radar transmission signal directly wraps around to the radar reception unit 200, the radar apparatus 10 does not perform processing by the correlation calculation unit 211 in a period (a period less than at least τ1) around which the radar transmission signal wraps around. Therefore, it becomes possible to perform measurement without the influence of wraparound. In addition, when the measurement range (range of k) is limited, the measurement range (range of k) is similarly limited for the processing of the addition unit 212, the Doppler frequency analysis unit 213, and the direction estimation unit 214 described below. It is sufficient to apply the above process. As a result, the amount of processing in each component can be reduced, and the power consumption of the radar receiver 200 can be reduced.

The adding unit 212 performs radar transmission of a predetermined number of times (Np times) using the correlation operation value AC _(z) (k, M) received from the correlation operation unit 211 for each discrete time k of the Mth radar transmission period Tr. The correlation operation value AC _(z) (k, M) is added (coherently integrated) over the period (Tr × Np) of the period Tr. The addition (coherent integration) process of the addition number Np over the period (Tr × Np) is expressed by the following equation.

Here, CI _(z) (k, m) represents an addition value of correlation operation values (hereinafter referred to as a correlation addition value), Np is an integer value of 1 or more, and m is the number Np of additions in the addition unit 212 It is an integer greater than or equal to 1 which shows the ordinal number of the addition frequency in, when 1 is made into 1 unit. Also, z = 1,..., Nt.

The addition unit 212 performs Np times of addition using the output of the correlation calculation unit 211 obtained on a radar transmission cycle Tr basis as one unit. That is, the adding unit 212 aligns the timing of the discrete time k with the correlation operation value AC _(z) (k, Np (m-1) + 1) to AC _(z) (k, Np x m) as one unit. The added correlation value CI _(z) (k, m) is calculated for each discrete time k. As a result, the addition unit 212 can improve the SNR of the reflected wave signal in a range where the reflected wave signal from the target has a high correlation by the effect of the addition of Np times of the correlation calculation value. Therefore, the radar receiving unit 200 can improve the measurement performance regarding estimation of the arrival distance of the target.

  In order to obtain an ideal addition gain, a condition is required in which the phase components of the correlation calculation value are aligned within a certain range in the addition section of the number Np of additions of the correlation calculation value. That is, the number of additions Np is preferably set based on the estimated maximum moving speed of the target to be measured. This is because the amount of fluctuation of the Doppler frequency included in the reflected wave from the target increases as the assumed maximum velocity of the target increases. For this reason, since the time period having high correlation becomes short, the number of additions Np becomes a small value, and the gain improvement effect by the addition in the addition unit 212 becomes small.

Doppler frequency analyzing unit 213, a Nc-number of the output of the adder 212 obtained for each discrete time _{k CI (z) (k,} Nc (w-1) +1) ~CI (z) (k, Nc Coherent integration is performed by aligning the timing of discrete time k with xw) as one unit. For example, the Doppler frequency analysis unit 213 performs coherent integration after correcting the phase fluctuation φ (fs) = 2πfs (Tr × Np) Δφ according to 2Nf different Doppler frequencies fsΔφ, as shown in the following equation.

Here, FT_CI _(z) ^Nant (k, fs, w) is the w-th output in the Doppler frequency analysis unit 213, and the Doppler frequency fsΔφ at the discrete time k in the Nant-th antenna system processing unit 201. The result of coherent integration is shown. However, Nant = 1 to Na, fs = -Nf + 1, ..., 0, ..., Nf, k = 1, ..., (Nr + Nu) Ns / No, and w is an integer of 1 or more, , Δφ are phase rotation units.

Thus, each antenna system processing unit 201 can obtain FT_CI _(z) ^Nant (k, -Nf + 1, w), ..., FT_CI ₍ coherent integration result according to 2Nf Doppler frequency components at discrete time k). _z) ^Nant (k, Nf-1, w) is obtained for each of multiple Np x Nc periods (Tr x Np x Nc) of the radar transmission period Tr. Here, j is an imaginary unit, and z = 1,..., Nt.

  When Δφ = 1 / Nc, the processing of the above-described Doppler frequency analysis unit 213 performs discrete Fourier transform (DFT) on the output of the addition unit 212 at the sampling interval Tm = (Tr × Np) and the sampling frequency fm = 1 / Tm. It is equivalent to processing.

Further, by setting Nf to the number of powers of 2, the Doppler frequency analysis unit 213 can apply fast Fourier transform (FFT) processing, and can reduce the amount of operation processing. If Nf> Nc, FFT processing can be applied in the same way by performing zero-filling processing in which CI _(z) (k, Nc (w-1) + q) = 0 in a region where q> Nc. The amount of arithmetic processing can be reduced.

Further, in the Doppler frequency analysis unit 213, instead of the FFT process, a process of sequentially calculating the product-sum operation shown in the above equation (4) may be performed. That is, the Doppler frequency analysis unit 213 applies fs to the CI _(z) (k, Nc (w-1) + q + 1) which is the Nc outputs of the addition unit 212 obtained for each discrete time k. The coefficients exp [-j2πf _s T _r N _p qΔφ] corresponding to = -Nf + 1, ..., 0, ..., Nf-1 may be generated and subjected to product-sum operation sequentially. Here, q = 0 to Nc-1.

In the following description, the w-th output FT_CI _(z) ¹ (k, fs, w), FT_CI _(z) ² obtained by performing the same processing in each of the Na antenna system processing units 201. (k, fs, w), ..., FT_CI _(z) ^Na (k, fs, w) is expressed as a virtual reception array correlation vector h (k, fs, w) as the following equation. The virtual reception array correlation vector h (k, fs, w) includes Nt × Na elements, which are the products of the number of transmitting antennas Nt and the number of receiving antennas Na. The virtual reception array correlation vector h (k, fs, w) is used for the process of performing direction estimation based on the phase difference between the receiving antennas 202 with respect to the reflected wave signal from the target, which will be described later. Here, z = 1,..., Nt and b = 1,.

  The process in each component of the signal processing unit 207 has been described above.

Direction estimating unit 214 transmits the transmit array antenna to virtual receive array correlation vector h (k, fs, w) of w-th Doppler frequency analysis unit 213 output from antenna system processing units 201-1 to 201-Na. A virtual reception array correlation vector _{h_after_cal in} which the phase deviation and the amplitude deviation between the antenna system processing units 201 are corrected by multiplying the array correction value h_cal _[y] for correcting the phase deviation and the amplitude deviation between the reception array antennas. Calculate (k, fs, w). The virtual reception array correlation vector _{h_after_cal} (k, fs, w) is expressed by the following equation. Note that y = 1,..., (Nt × Na).

A virtual reception array correlation vector _{h_after_cal} (k, fs, w) corrected for the deviation between antennas is a column vector consisting of Na × Nt elements. In the following, each element of the virtual reception array correlation vector _{h_after_cal} (k, fs, w) is written as h ₁ (k, fs, w), ..., h _{Nt × Na} (k, fs, w) Used to explain the estimation process.

  The direction estimation unit 214 performs arrival direction estimation processing in the horizontal direction and the vertical direction based on the phase difference between the reception antennas of the incoming reflected wave.

[Method of Estimating Direction of Arrival in Radar Device 10]
Details of the direction of arrival estimation method in the radar device 10 having the above configuration will be described.

  FIG. 6 is a block diagram showing an example of an internal configuration of the direction estimation unit 214 (arrival direction estimation device) in the radar device 100 shown in FIG.

  In the following description, the number of incoming waves (hereinafter, referred to as NW) in the radar device 10 is assumed to be two waves. That is, the direction estimation unit 214 estimates the arrival angles of two waves in the horizontal and vertical two-dimensional planes. The number of incoming waves NW is not limited to two, and may be one or three or more.

  The direction estimating unit 214 shown in FIG. 6 includes an inter-antenna deviation correcting unit 241, a horizontal array maximum likelihood estimating unit 242, a vertical array maximum likelihood estimating unit 243, and a horizontal / vertical maximum likelihood estimating unit 244. Have.

As described above, the inter-antenna deviation correction unit 241 applies to the virtual reception array correlation vector h (k, fs, w) of the Doppler frequency analysis unit 213 output from the antenna system processing units 201-1 to 201-Na. The phase deviation and the amplitude deviation between the antenna system processing units 201 are corrected by multiplying the array correction value h_cal _[y] (see, for example, equation (7)).

<Operation of Horizontal Direction Array Maximum Likelihood Estimator 242>
The horizontal array maximum likelihood estimation unit 242 performs the following processing based on the virtual reception array correlation vector _{h_after_cal} (k, fs, w) corrected from the inter-antenna deviation, which is input from the inter-antenna deviation correction unit 241. .

Specifically, first, the horizontal array maximum likelihood estimation unit 242 _calculates the virtual reception antennas VA # 1,..., Included in the virtual reception array correlation vector _{h_after_cal} (k, fs, w) obtained by correcting the inter-antenna deviation. A horizontal array correlation vector h _SubH (consisting of elements of a virtual horizontal linear array constituting a linear array of three or more antennas in the horizontal direction on the virtual reception array) from elements respectively corresponding to VA # (Nt × Na) Extract k, fs, w). In the following, it is assumed that the number of elements constituting each of the virtual horizontal linear arrays (that is, the number of virtual reception antennas) is “N _VAH ” (here, N _VAH is a value of 3 or more).

Then, the horizontal array maximum likelihood estimation unit 242 performs maximum likelihood estimation processing in the horizontal direction using the extracted horizontal array correlation vector h _SubH (k, fs, w). In the horizontal maximum likelihood estimation, the horizontal array maximum likelihood estimation unit 242 determines a predetermined evaluation function E _SubH (θ ⁽¹⁾ , θ ^{(2 )} based on the principle of maximum likelihood estimation within a predetermined horizontal search grid. ^The angle (maximum likelihood value) at which the _, ..., Θ ^(NW) ) becomes minimum or maximum is calculated. Here, NW represents the number of incoming waves.

The number of incoming waves NW may be fixed in advance or may be adaptively varied using a virtual reception array correlation vector _{h_after_cal} (k, fs, w). For estimation of the number of incoming waves, MDL (Minimum Description Length) or AIC (Akaike Information Criteria) may be used.

  Further, the number of antennas constituting the virtual horizontal linear array on the virtual reception array is not limited to 3 antennas, and the virtual horizontal linear array is at least (NW + 1) virtual reception antennas according to the number of incoming waves NW. It should just be comprised.

When there are a plurality of virtual horizontal direction linear arrays constituting a linear array of three or more antennas in the horizontal direction on the virtual reception array, the horizontal direction array maximum likelihood estimation unit 242 determines the elements included in each virtual horizontal direction linear array , H _{SubH (1)} (k, fs, w), h _{SubH (2)} (k, fs, w),..., H _{SubH (NsubH)} (k, An angle (maximum likelihood) at which a predetermined evaluation function E _SubH (θ ⁽¹⁾ , θ ⁽²⁾ _, ..., θ ^(NW) ) is minimum or maximum based on the principle of maximum likelihood estimation using fs, w)} Calculate the value). Here, the number of virtual horizontal direction linear arrays of three or more antennas in the horizontal direction on the virtual reception array (the number of horizontal array correlation vectors) is _assumed to be “N _subH ”.

Also, as the predetermined evaluation function E _SubH (θ ⁽¹⁾ , θ ⁽²⁾ _, ..., θ ^(NW) ) based on the principle of maximum likelihood estimation, for example, the following equations (8), (9), and (10) Can be used.

Here, a _SubH (θ _u , α _SH ) represents a horizontal array direction vector, and elements VA # 1 to VA # (Nt included in virtual reception array correlation vector _{h_after_cal} (k, fs, w) Among Na), it is a direction vector obtained by extracting a component corresponding to an element of the virtual horizontal direction straight line array from the direction vector a (θ _u , φ _v ) of the virtual reception array. Note that α _SH is a fixed direction, and may be, for example, the 0 ° direction or another direction.

In equation (8), the evaluation function ^{_{E SubH (θ (1),}} θ (2), ..., θ (NW)) to minimize the angle ^{(θ (1), θ (} 2), ..., θ (NW) ) Is the maximum likelihood value. The horizontal array maximum likelihood estimation unit 242 determines the angles (θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ _, ..., Θ _ML ^(NW) ) which become maximum likelihood values in the horizontal search grid in the horizontal / vertical directions. It outputs to the likelihood estimation unit 244.

As shown in equation (8), the horizontal array maximum likelihood estimation unit 242 receives a plurality of (N _subH ) virtual horizontal linear array reception signals (horizontal array correlation vector h _SubH (k, fs, w)) By using, it is possible to improve the reception quality (for example, SNR) and calculate the maximum likelihood value. When the reception quality in the radar device 10 is sufficiently good, the horizontal direction array maximum likelihood estimation unit 242 determines that a predetermined number (at least one) of virtual horizontal direction linear arrays of the plurality of virtual horizontal direction linear arrays are present. The maximum likelihood value may be calculated using the received signal of As a result, the amount of computation can be reduced while maintaining the reception quality.

Also, the direction vector a (θ _u , φ _v ) is an (Nt × Na) -order column vector whose element is the complex response of the virtual reception array antenna when the radar reflected wave arrives from the azimuth direction θ and the elevation direction φ. It is. The complex response a (θ _u , φ _v ) of the virtual reception array antenna represents the phase difference calculated geometrically by the element spacing between the antennas.

That is, the complex response a (θ _u , φ _v ) of the virtual reception array antenna is a value uniquely calculated if the virtual reception array arrangement in the radar device 10 is determined. Therefore, horizontal direction array maximum likelihood estimation unit 242 calculates direction vector a (θ _u , φ _v ) in advance based on virtual reception array arrangement VA # 1,..., VA # (Nt × Na), and stores it. May be

Alternatively, the horizontal array maximum likelihood estimation unit 242 measures the complex response of the virtual reception array antenna when the radar reflected wave arrives from the azimuth direction θ and the elevation direction φ as a direction vector a (θ _u , φ _v ) May be stored. In this case, since the direction vector a (θ _u , φ _v ) includes a deviation depending on the direction between the array antennas, the direction estimation unit 214 is ideally deviated from the phase calculated geometrically optically Can be corrected at the same time, and more accurate angle measurement processing becomes possible.

In addition, among the parameters used in the evaluation function, the direction vector a (theta _u, is a parameter related to phi _v, is included in the formula _{(10) (A SubH (ns} ) H A SubH (ns)) -1 A SubH _(ns) ^H is a value determined depending on the virtual reception array arrangement, and is a fixed value for each angle The horizontal array maximum likelihood estimator 242 _{calculates (} A _{SubH (ns)} ^H A _{SubH (ns ) ^{the)) -1 a SubH (ns)}} H, may be calculated for each angle in the horizontal direction of the search grid. or horizontal array maximum likelihood estimator ^{_{242, (a SubH (ns) H}} a SubH ( _ns) ) ^-1 A _Sub ^H _(ns) The calculation result of ^H may be stored in advance and _tabulated , and a configuration may be used to read out for each angle, which makes part of the calculation processing shown in equation (10) unnecessary. It can reduce the amount of calculation. in the case of using the structure of reading for each angle, it is required a memory circuit for storing the ^{_{(a SubH (ns) H a}} SubH (ns)) -1 a SubH (ns) H , It is possible to reduce arithmetic circuits such as multipliers or adders.

Further, θ _u is a vector in which the horizontal (or azimuth) range in which the arrival direction is estimated is changed at a predetermined horizontal (or azimuth) interval β ₁ . For example, θ _u is set as follows.
θ _u = θ min + _u β ₁ , u = 0, ..., NU
NU = floor [(θmax−θmin) / β ₁ ] +1
Here, floor (x) is a function that returns the largest integer value not exceeding real number x.

Also, φ _v is a vector in which the vertical (or elevation) range in which the direction of arrival estimation is performed is changed at a predetermined vertical (or elevation) interval β ₂ . For example, φ _v is set as follows.
φ v = φ min + v β ₂ , v = 0, ..., NV.
NV = floor [(φmax−φmin) / β ₂ ] +1

Therefore, the horizontal array maximum likelihood estimation unit 242 determines each of θ ⁽¹⁾ , θ ⁽²⁾ _, ..., θ ^{(in the} search grid consisting of horizontal (azimuth) intervals β ₁ from the minimum azimuth θ min to the maximum azimuth θ max ⁾ _. Search the ^NW) .

The following equation (11) may be used as another example of the predetermined evaluation function E _SubH (θ ⁽¹⁾ , θ ⁽²⁾ _, ..., Θ ^(NW) ) based on the principle of maximum likelihood estimation. In Equation (11), the angle that maximizes the evaluation function E _SubH (θ ⁽¹⁾ , θ ⁽²⁾ _, ..., Θ ^(NW) ) is the maximum likelihood value. The horizontal array maximum likelihood estimation unit 242 outputs angles (θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ _, ..., Θ _ML ^(NW) ) which become maximum likelihood values in the horizontal search grid.

  Here, as an example, an operation of the horizontal array maximum likelihood estimation unit 242 in the arrangement example of the transmission antenna 106 and the reception antenna 202 illustrated in FIG. 7A will be described.

  In FIG. 7A, the number Nt of transmitting antennas 106 is three, and the number Na of receiving antennas 202 is three. Also, three transmit antennas 106 are represented by Tx # 1 to Tx # 3, and three receive antennas 202 are represented by Rx # 1 to Rx # 3. 7B shows the arrangement of virtual reception arrays obtained by the antenna arrangement shown in FIG. 7A.

In the virtual reception array shown in FIG. 7B, the horizontal and vertical aperture lengths D _H and D _V of the antenna are D _H = 2 d _H and D _V = 2 d _V , respectively. Here, d _H is an element interval in the horizontal direction, and d _V is an element interval in the vertical direction.

In the virtual reception array shown in FIG. 7B, there are three virtual horizontal direction linear arrays of N _VAH = 3 (that is, N _subH = 3), and horizontal array correlation vectors respectively corresponding to the virtual horizontal direction linear arrays {H _{SubH (1)} (k, fs, w), h _{SubH (2)} (k, fs, w), h _{SubH (3)} (k, fs, w)} are obtained. Specifically, in FIG. 7B, each horizontal array correlation vector {h _{SubH (1)} (k, fs, w), h _{SubH (2)} (k, fs, w), h _{SubH (3)} (k, The element numbers of the virtual reception array correlation vector _{h_after_cal} (k, fs, w) included in fs, w)} are {VA # 1, VA # 4, VA # 7}, {VA # 2, VA # 5, respectively. , VA # 8}, {VA # 3, VA # 6, VA # 9}.

Horizontal direction corresponding to horizontal array correlation vector {h _{SubH (1)} (k, fs, w), h _{SubH (2)} (k, fs, w), h _{SubH (3)} (k, fs, w)} Array direction vectors {a _{SubH (1)} (θ _u , α), a _{Sub H (2)} (θ _u , α), a _{Sub H (3)} (θ _u , α)} are the direction vectors of the virtual reception array a ( Element numbers of θ _u and φ _v ) {VA # 1, VA # 4, VA # 7}, {VA # 2, VA # 5, VA # 8}, {VA # 3, VA # 6, VA # 9} These are column vectors constructed by extracting each of

The horizontal array maximum likelihood estimator 242 _calculates horizontal array correlation vectors {h _{SubH (1)} (k, fs, w), h _{SubH (2)} (k, fs, w), h _{SubH (3)} (k, An angle (θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ ) (ie, horizontal) at which the evaluation function E _SubH (eg, equation (8) or (11)) becomes minimum or maximum, using fs, w)} Extract NW = 2 arrival angle candidates in the direction).

As described above, the horizontal array maximum likelihood estimation unit 242 determines the plurality of virtual reception antennas included in the virtual reception array configured based on the arrangement of the transmission array antenna (transmission antenna 106) and the reception array antenna (reception antenna 202). Of (VA # 1 to VA # 9 in FIG. 7B), reception signals (virtual reception array correlation vectors) of a virtual horizontal direction linear array configured by virtual reception antennas linearly arranged in the horizontal direction are used. Maximum likelihood values (θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ ) corresponding to NW angles (here, NW = 2) in the horizontal direction are extracted by maximum likelihood estimation processing in the horizontal direction.

<Operation of Vertical Direction Array Maximum Likelihood Estimator 243>
The vertical array maximum likelihood estimation unit 243 performs the following processing based on the virtual reception array correlation vector _{h_after_cal} (k, fs, w) corrected from the inter-antenna deviation, which is input from the inter-antenna deviation correction unit 241. .

Specifically, first, the vertical array maximum likelihood estimation unit 243 determines the virtual reception antennas VA # 1,..., Included in the virtual reception array correlation vector _{h_after_cal} (k, fs, w) in which the deviation between antennas is corrected. A vertical array correlation vector h _SubV (consisting of elements of a virtual vertical linear array constituting a linear array of three or more antennas in the vertical direction on the virtual reception array) from elements respectively corresponding to VA # (Nt × Na) Extract k, fs, w). In the following, it is assumed that the number of elements constituting each of the virtual vertical direction linear arrays (that is, the number of virtual reception antennas) is “N _VAV ” (here, N _VAV is a value of 3 or more).

Then, the vertical array maximum likelihood estimation unit 243 performs maximum likelihood estimation processing in the vertical direction using the vertical array correlation vector h _SubV (k, fs, w) composed of the elements of the extracted virtual vertical straight line array. . In the vertical maximum likelihood estimation, the vertical array maximum likelihood estimation unit 243 determines a predetermined evaluation function E _SubV (φ ⁽¹⁾ , φ ^{(2 )} based on the principle of maximum likelihood estimation within a predetermined vertical search grid. _^), ..., and calculates the phi ^(NW)) angle is the minimum or maximum (maximum likelihood value). Here, NW represents the number of incoming waves.

  The number of antennas constituting the virtual vertical direction linear array on the virtual reception array is not limited to three, and the virtual vertical direction linear array is at least (NW + 1) virtual reception antennas according to the number of incoming waves NW. It should just be comprised.

Further, when there are a plurality of virtual vertical direction linear arrays constituting a linear array of three or more antennas in the vertical direction on the virtual reception array, the vertical direction array maximum likelihood estimation unit 243 determines the elements included in each virtual vertical direction linear array A plurality of vertical array correlation vectors {h _{SubV (1)} (k, fs, w), h _{SubV (2)} (k, fs, w), ..., h _{SubV (NsubV)} (k, An angle (maximum likelihood) at which a predetermined evaluation function E _SubV (φ ⁽¹⁾ , φ ⁽²⁾ _, ..., φ ^(NW) ) is minimum or maximum based on the principle of maximum likelihood estimation using fs, w)} Calculate the value). Here, the number of virtual vertical direction linear arrays of three or more antennas in the vertical direction on the virtual reception array (the number of vertical array correlation vectors) is _assumed to be “N _subV ”.

Also, as predetermined evaluation functions E _SubV (φ ⁽¹⁾ , φ ⁽²⁾ _, ..., φ ^(NW) ) based on the principle of maximum likelihood estimation, for example, the following equations (12), (13), (14) Can be used.

_{Here, a SubV (α SV, φ} ν) denotes a vertical array direction vector, elements VA # 1 included in the virtual receiving array correlation vector _{h _after_cal (k, fs, w} ), ..., VA # (Nt Among Na), it is a direction vector obtained by extracting a component corresponding to an element of the virtual vertical direction straight line array from the direction vector a (θ _u , φ _v ) of the virtual reception array. Here, α _SV is a fixed direction, and may be, for example, the 0 ° direction or another direction.

In equation (12), the evaluation function ^{_{E SubV (φ (1),}} φ (2), ..., φ (NW)) angle that minimizes ^{(φ (1), φ (} 2), ..., φ (NW) ) Is the maximum likelihood value.

The vertical array maximum likelihood estimation unit 243, for example, the range of the maximum azimuth φmax minimum azimuth φmin perpendicular each in the search grid of (elevation angle) intervals ^{_{β 2 φ (1), φ}} (2), ..., φ ( Search the ^NW) . Then, the vertical array maximum likelihood estimation unit 243 determines the angles (φ ⁽¹⁾ , φ ⁽²⁾ _, ..., φ ^(NW) ) that are the maximum likelihood values in the search grid in the vertical direction in the horizontal / vertical directions. It is output to the estimation unit 244.

Also, as shown in equation (12), the vertical direction array maximum likelihood estimation unit 243 is configured to receive received signals (vertical direction array correlation vector h _SubV (k, fs, w) of a plurality (N _subV pieces) of virtual vertical direction linear arrays. By using), the reception quality (for example, SNR) can be improved and the maximum likelihood value can be calculated. When the reception quality in the radar device 10 is sufficiently good, the vertical direction array maximum likelihood estimation unit 243 determines a predetermined number (at least one) of the virtual vertical direction linear arrays of the plurality of virtual vertical direction linear arrays. The maximum likelihood value may be calculated using the received signal of As a result, the amount of computation can be reduced while maintaining the reception quality.

In addition, among the parameters used in the evaluation function, the direction vector a (theta _u, is a parameter related to phi _v, is included in the formula _{(14) (A SubV (ns} ) H A SubV (ns)) -1 A SubV _(ns) ^H is a value determined depending on the virtual reception array arrangement, and is a fixed value for each angle The vertical array maximum likelihood estimator 243 _{calculates (} A _{SubV (ns)} ^H A _{SubV (ns ) ))} the ^-1 a _{SubV (ns)} ^H, may be calculated for each angle in the vertical direction of the search grid. or vertical array maximum likelihood estimator ^{_{243, (a SubV (ns) H}} a SubV ( _ns) ) ^-1 A _{SubV (ns)} The calculation result of ^H may be stored in advance and _tabulated , and a configuration may be used to read out for each angle, which makes part of the calculation processing shown in equation (14) unnecessary. It can reduce the amount of calculation. in the case of using the structure of reading for each angle, it is required a memory circuit for storing the ^{_{(a SubV (ns) H a}} SubV (ns)) -1 a SubV (ns) H , It is possible to reduce arithmetic circuits such as multipliers or adders.

The following equation (15) may be used as another example of the predetermined evaluation function E _SubV (φ ⁽¹⁾ , φ ⁽²⁾ _, ..., φ ^(NW) ) based on the principle of maximum likelihood estimation. In Equation (15), the _{angle maximizing} the evaluation function E _SubV (φ ⁽¹⁾ , φ ⁽²⁾ _, ..., φ ^(NW) ) is the maximum likelihood value. The vertical array maximum likelihood estimation unit 243 outputs angles (φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ _, ..., Φ _ML ^(NW) ) which become maximum likelihood values in the search grid in the vertical direction.

  Here, as an example, an operation of the horizontal array maximum likelihood estimation unit 242 in the arrangement example of the transmitting antenna 106 and the receiving antenna 202 illustrated in FIGS. 7A and 7B will be described.

The virtual reception array shown in FIG. 7B, N _VAV = 3 virtual vertical linear array is three _(i.e., N subV = 3) is present, the corresponding vertical array correlated to each virtual vertical linear array The vectors {h _{SubV (1)} (k, fs, w), h _{SubV (2)} (k, fs, w), h _{SubV (3)} (k, fs, w)} are obtained. Specifically, in FIG. 7B, each vertical array correlation vector {h _{SubV (1)} (k, fs, w), h _{SubV (2)} (k, fs, w), h _{SubV (3)} (k, The element numbers of the virtual reception array correlation vector h _{_after_cal} (k, fs, w) included in fs, w)} are {VA # 1, VA # 2, VA # 3} and {VA # 4, VA # 5, respectively. It is VA # 6}, {VA # 7, VA # 8, VA # 9}.

Vertical direction corresponding to vertical array correlation vector {h _{SubV (1)} (k, fs, w), h _{SubV (2)} (k, fs, w), h _{SubV (3)} (k, fs, w)} array direction vector _{{a SubV (1) (α} SV, φ ν), a SubV (2) (α SV, φ ν), a SubV (3) (α SV, φ ν)} , the direction of the virtual receiving array Element numbers {VA # 1, VA # 2, VA # 3}, {VA # 4, VA # 5, VA # 6}, {VA # 7, VA # 8, VA of vector a (θ _u , φ _v ) It is a column vector configured by extracting # 9}.

The vertical array maximum likelihood estimation unit 243 determines the vertical array correlation vector {h _{SubV (1)} (k, fs, w), h _{SubV (2)} (k, fs, w), h _{SubV (3)} (k, The angle (φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ ) (ie, vertical) at which the evaluation function E _SubV (eg, equation (12) or equation (15)) becomes minimum or maximum, using fs, w)} Extract NW = 2 arrival angle candidates in the direction).

As described above, the vertical array maximum likelihood estimation unit 243 includes a plurality of virtual reception antennas included in a virtual reception array configured based on the arrangement of the transmission array antenna (transmission antenna 106) and the reception array antenna (reception antenna 202). Of (VA # 1 to VA # 9 in FIG. 7B), reception signals (virtual reception array correlation vectors) of a virtual vertical direction linear array configured by virtual reception antennas linearly arranged in the vertical direction are used. Maximum likelihood values (φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ ) corresponding to NW angles in the vertical direction are extracted by maximum likelihood estimation processing in the vertical direction.

  That is, each of the horizontal array maximum likelihood estimation unit 242 and the vertical array maximum likelihood estimation unit 243 performs maximum likelihood estimation processing in one dimension direction in the horizontal direction and the vertical direction.

<Operation of Horizontal / Vertical Maximum Likelihood Estimator 244>
The horizontal / vertical maximum likelihood estimation unit 244 outputs an output result (θ _ML ⁽ horizontal arrival angle candidate) which is the maximum likelihood value (horizontal arrival angle candidate) within the horizontal search grid, which is input from the horizontal array maximum likelihood estimation unit 242. ¹⁾ , θ _ML ⁽²⁾ _, ..., Θ _ML ^(NW) and maximum likelihood values (vertical arrival angle candidates in the vertical search grid, which are input from the vertical array maximum likelihood estimation unit 243 Using the output results (φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ _, ..., Φ _ML ^(NW) ) to be the), the arrival directions of NW arrival waves in a two-dimensional plane spreading in the horizontal and vertical directions ( θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., θ ^(NW) , φ ^(NW ) are estimated.

Specifically, the horizontal / vertical maximum likelihood estimation unit 244 determines the arrival angle (θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ _, ..., Θ _ML ^(NW) ) corresponding to the horizontal maximum likelihood value and the vertical The combination of arrival angles (φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ _, ..., φ _ML ^(NW) ) corresponding to the maximum likelihood value of the direction is the search angle candidate and the search grid is limited in the horizontal and vertical directions 2 Perform maximum likelihood estimation process of dimension.

Maximum likelihood values θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ _, ..., θ _ML ^(NW) in the horizontal direction, and maximum likelihood values φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ _, ..., φ _{ML in the} vertical direction ^{In the} case where there is no overlap in the two-dimensional plane extending in the horizontal direction and the vertical direction, (NW) constitutes at most (NW × NW) lattice points.

  The horizontal / vertical maximum likelihood estimation unit 244 estimates the maximum likelihood value using the maximum (NW × NW) grid points. That is, the horizontal / vertical maximum likelihood estimation unit 244 performs two-dimensional maximum likelihood estimation processing in the horizontal and vertical directions using the limited range of the maximum (NW × NW) grid points as a search grid.

Therefore, the horizontal / vertical maximum likelihood estimation unit 244 searches for NW different combinations from (NW × NW) grid points. Therefore, _{(Nw × Nw)} C _Nw combinations of θ and φ become the number of searches of the two-dimensional maximum likelihood estimation in the horizontal direction and the vertical direction.

  For example, FIG. 8 shows a search grid in the case of the number of incoming waves NW = 2.

In the example of FIG. 8, four lattice points are obtained from the maximum likelihood values θ _ML ⁽¹⁾ and θ _ML ⁽²⁾ in the horizontal direction and the maximum likelihood values φ _ML ⁽¹⁾ and φ _ML ^{(2) in} the vertical direction. Exists. As shown in FIG. 8, all combinations for searching two different grid points from four grid points are six combinations (= ₄ C ₂ ).

In horizontal and vertical two-dimensional maximum likelihood estimation, the horizontal / vertical maximum likelihood estimation unit 244 uses the virtual reception array correlation vector _{h_after_cal} (k, fs, w) corrected for the inter-antenna deviation to The predetermined evaluation function E _ML2D (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., θ ^(NW) , φ ^(NW) ) based on the principle of likelihood estimation is the minimum or maximum The angles (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., Θ ^(NW) , φ ^(NW) ) are extracted.

As a predetermined evaluation function E _ML2D (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., θ ^(NW) , φ ^(NW) ) based on the principle of maximum likelihood estimation, for example, The following equations (16), (17) and (18) can be used.

Here, a (θ _u , φ _v ) represents the direction vector of the virtual reception array. In equation (16), the angle (θ) that minimizes the evaluation function E _ML2D (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., θ ^(NW) , φ ^(NW) ) ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., θ ^(NW) , φ ^(NW ) are two-dimensional maximum likelihood values in the horizontal direction and the vertical direction.

The horizontal / vertical maximum likelihood estimation unit 244 _calculates θ _ML 2 D ⁽¹⁾ , φ _ML ² _D ⁽¹⁾ , θ _ML ² _D ⁽²⁾ _, φ that is the two-dimensional maximum likelihood value in the horizontal direction and the vertical direction within the limited search grid. _ML2D ⁽²⁾ _, ..., θ _ML2D ^(NW) , φ _ML2D ^(NW) are output. Also, the horizontal / vertical maximum likelihood estimation unit 244 estimates the calculated values of the arrival angle (θ _ML2D ⁽¹⁾ , φ _ML2D ⁽¹⁾ , θ _ML2D ⁽²⁾ _, φ _ML2D ⁽²⁾ _, ..., Θ _ML2D ^{In addition to (NW)} , φ _ML2D ^(NW) , the discrete time k at that time and the Doppler frequency fsΔφ may be output as the arrival direction estimation result.

In the example of FIG. 8, the horizontal / vertical maximum likelihood estimation unit 244 determines the direction θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ (arrival angle candidate) corresponding to the horizontal maximum likelihood value and the maximum likelihood in the vertical direction. Among the combinations of directions φ _ML ⁽¹⁾ and φ _ML ⁽²⁾ (arrival angle candidates) corresponding to the values, the arrival angles of NW = 2 arrival waves in a two-dimensional plane are determined. Specifically, the horizontal / vertical maximum likelihood estimation unit 244 can estimate the horizontal arrival angle (θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ ) and the vertical arrival angle (φ _ML ⁽¹⁾ , φ A direction corresponding to the maximum likelihood value obtained by performing maximum likelihood estimation processing on a two-dimensional plane with respect to the combination of _ML ⁽²⁾ ) is the angle of arrival (θ ⁽¹⁾ , φ ^{(1 _), θ (2),} is estimated as φ ^(2)).

Note that among the parameters used for the evaluation function, (A _ML ^H A _ML ) ⁻¹ A _ML ^H included in equation (16), which is a parameter related to the direction vector a (θ _u , φ _v ), is a virtual reception array It is a value determined depending on the arrangement, and is a fixed value for each angle.The horizontal / vertical maximum likelihood estimator 244 calculates (A _ML ^H A _ML ) ⁻¹ A _ML ^H in the horizontal and vertical directions. The horizontal / vertical maximum likelihood estimation unit 244 may store in advance the calculation results of (A _ML ^H A _ML ) ⁻¹ A _ML ^H and make a table, may be used an arrangement for reading in each angle. Accordingly, it is possible to reduce the amount of calculation portion becomes unnecessary arithmetic processing of equation (18). in the case of using the structure of reading for each angle, (a _ML ^H a _ML ¹ ) A memory circuit for storing _AML ^H is required, but arithmetic circuits such as multipliers or adders can be reduced. And is possible.

Note that other predetermined evaluation functions E _ML2D (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., θ ^(NW) , φ ^(NW) ) based on the principle of maximum likelihood estimation The following equation (19) may be used as an example of In equation (19), the _{angle maximizing} the evaluation function E _ML2D (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., θ ^(NW) , φ ^(NW) ) is horizontal Two-dimensional maximum likelihood value in the direction and vertical direction. Horizontal / vertical maximum likelihood estimator 244, the maximum likelihood value of two-dimensional horizontal and vertical directions in limited were the search grid as described above ^{_{θ ML2D (1), φ ML2D}} (1), θ ML2D ( ²⁾ _, φ _ML2D ⁽²⁾ _, ..., θ _ML2D ^(NW) , φ _ML2D ^(NW) are output.

  The operation of the direction estimation unit 214 has been described above.

  As described above, in the direction estimation unit 214, each of the horizontal array maximum likelihood estimation unit 242 and the vertical array maximum likelihood estimation unit 243 performs maximum likelihood estimation processing in the search grid in the horizontal direction or the vertical direction. I do. Then, the horizontal / vertical maximum likelihood estimation unit 244 determines the horizontal direction and the horizontal direction based on the maximum likelihood value in the search grid in the one-dimensional direction in the horizontal array maximum likelihood estimation unit 242 and the vertical array maximum likelihood estimation unit 243. A search grid in a two-dimensional plane extending in the vertical direction is limited, and maximum likelihood estimation processing is performed in the limited search grid.

  That is, the direction estimation unit 214 performs maximum likelihood estimation processing separately in two steps of each one-dimensional direction in the horizontal direction and the vertical direction and a two-dimensional plane in the horizontal direction and the vertical direction. Thereby, in the present embodiment, the number of searches (the amount of operation) is significantly reduced compared to the case where the two-dimensional maximum likelihood estimation processing is performed in all the search grids in the horizontal direction and the vertical direction (conventional method). can do.

  For example, the case where the number of search grids in the horizontal direction is NGH and the number of search grids in the vertical direction is NGV will be described.

In this case, in the present embodiment, the sum of the number of searches in the horizontal array maximum likelihood estimator 242 and the vertical array maximum likelihood estimator 243 is ( _(NGH) C _NW + _(NGV) C _NW ) times. . Furthermore, the horizontal / vertical maximum likelihood estimation unit 244 limits the search range to the angular range to which the horizontal array maximum likelihood estimation unit 242 and the vertical array maximum likelihood estimation unit 243 are output. The number of searches in the estimation unit 244 is _{(Nw × Nw)} C _Nw times.

On the other hand, the number of searches of the conventional method using a two-dimensional search grid in the horizontal direction and the vertical direction is ( _{(NGV × NGH)} C _NW ) times.

Therefore, in the present embodiment, the reduction ratio is roughly {(NGV ^NW + NGH ^NW ) / (NGV × NGH) ^NW } compared to the conventional method. For example, in the case of NGV = NGH = N, the method according to the present embodiment has a reduction ratio of 2 / N ^{NW with} respect to the conventional method. For example, in the case of N = 10 and NW = 2, the number of searches can be reduced to about 1/50 that of the conventional method.

  In addition, as the number of search grids NGH and NGV is larger, or as the number of incoming waves NW is larger, the effect of reducing the number of searches according to the present embodiment becomes larger.

  FIG. 9 shows an example of the number of searches for the number of search grids NGV = NGH = N when the number of incoming waves NW = 2. As shown in FIG. 9, according to the method (the present disclosure) according to the present embodiment, it can be confirmed that the number of searches is reduced compared to the conventional method. Further, as shown in FIG. 9, it can be confirmed that the reduction effect of the number of searches according to the present embodiment becomes larger as the number N of search grids (NGH, NGV) increases.

  FIG. 10 shows an example of the reduction ratio of the number of searches to the conventional method by the method according to the present embodiment with respect to the number of search grids NGV = NGH = N when the number of incoming waves NW = 2 and 3. As shown in FIG. 10, it can be confirmed that the reduction effect of the number of searches according to the present embodiment becomes larger as the number N of search grids (NGH, NGV) increases and as the number of incoming waves NW increases.

  As described above, according to the present embodiment, when the radar device 10 estimates the direction of arrival using the maximum likelihood estimation method, the number of searches is reduced, thereby suppressing an increase in the amount of computation and achieving high It can be measured to the accuracy.

(Variation 1 of Embodiment)
The above embodiment has described the case where the maximum likelihood value is output as the maximum likelihood estimation result in the horizontal direction or the vertical direction, and the maximum likelihood estimation process in the two-dimensional direction is performed. On the other hand, in the variation 1, as the maximum likelihood estimation result in the horizontal or vertical one-dimensional direction, in addition to the maximum likelihood value, an angle candidate other than the maximum likelihood value is output and output. The case of performing the likelihood estimation process will be described.

  FIG. 11 is a block diagram showing an example of an internal configuration of the direction estimation unit 214 according to the variation 1. In FIG. 11, the same components as those in the above embodiment (FIG. 6) will be assigned the same reference numerals and descriptions thereof will be omitted.

  Below, the case where the number of arrival waves with respect to the radar apparatus 10 (FIG. 2) is made into two waves (NW = 2) as an example is demonstrated.

<Operation of Horizontal Direction Array Maximum Likelihood Candidate Extraction Unit 301>
In FIG. 11, the horizontal array maximum likelihood candidate extraction unit 301 inputs the following based on the virtual reception array correlation vector _{h_after_cal} (k, fs, w) corrected from the inter-antenna deviation, which is input from the inter-antenna deviation correction unit 241. Perform the processing of

Specifically, first, the horizontal array maximum likelihood candidate extraction unit 301 _calculates the virtual reception antennas VA # 1,..., _Which are included in the virtual reception array correlation vector _{h_after_cal} (k, fs, w) in which the deviation between antennas is corrected. , VA # (Nt × Na), and a horizontal array correlation vector h _SubH (composed of horizontal linear array elements constituting a linear array of three or more antennas in the horizontal direction on the virtual reception array). Extract k, fs, w).

Then, the horizontal array maximum likelihood candidate extraction unit 301 performs maximum likelihood estimation processing in the horizontal direction using the extracted horizontal array correlation vector h _SubH (k, fs, w). In the horizontal maximum likelihood estimation, the horizontal array maximum likelihood candidate extraction unit 301 determines a predetermined evaluation function E _SubH (θ ⁽¹⁾ , θ ⁽ maximum ⁾ based on the principle of maximum likelihood estimation within a predetermined horizontal search grid. ²⁾ Calculate the angle (maximum likelihood value) at which the _, ..., Θ ^(NW) ) becomes minimum or maximum. In the variation 1, the horizontal array maximum likelihood candidate extraction unit 301 adds local areas other than the maximum likelihood value of the evaluation function used for the maximum likelihood estimation process in the horizontal direction in addition to the maximum likelihood values (corresponding to NW angles). The maximum likelihood value (extreme value) (each corresponding to NW angles) is extracted. Then, the horizontal array maximum likelihood candidate extraction unit 301 respectively corresponds to NW angles corresponding to the maximum likelihood value and at least one local maximum likelihood value (extreme value) other than the maximum likelihood value in the evaluation function. Horizontal arrival angle candidates (maximum likelihood candidates) including NW angles are output to the horizontal / vertical maximum likelihood estimation unit 303.

  The angle that is the local maximum likelihood value is, for example, a value that satisfies the following condition.

1) When the Minimum Value of a Predetermined Evaluation Function Based on the Principle of Maximum Likelihood Estimation Becomes the Maximum Likelihood Value The horizontal direction array maximum likelihood candidate extraction unit 301 determines the local minimum value (minimum value) satisfying the condition ^{_{value) E subH (θ (1)}} , θ (2), ..., θ (NW)) angle ^(θ _NHLocalML ⁽¹⁾ to _{^{give, θ NHLocalML (2), ...}} , to extract θ _NHLocalML ^(NW)).
E _subH (θ ⁽¹⁾ , θ ⁽²⁾ _, ..., θ ^(NW) ) <α _H × E _HML (20)

However, it is NHLocalML = 1, ..., N _HLM . Also, E _HML is the minimum value (maximum likelihood value) [θ _ML ⁽¹⁾ of the evaluation function E _SubH (θ ⁽¹⁾ , θ ⁽²⁾ _, ..., θ ^(NW) ) in a predetermined search grid in the horizontal direction , θ _ML ⁽²⁾ _, ..., θ _ML ^(NW) ]. Further, α _H is a predetermined value (α _H > 1). That is, the following equation (21) is satisfied.
E _HML = E _{sub H} (θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ _, ..., θ _ML ^(NW) ) (21)

When the local minimum value satisfying the condition shown in equation (20) exceeds the predetermined number N _H (N _HLM > N _H ), the horizontal array maximum likelihood candidate extraction unit 301 evaluates the evaluation function E _SubH (θ ^{(1) _{, θ (2), ...,}} θ (NW)) to the smaller value may output N _H following candidates and priority.

2) When the Maximum Value of a Predetermined Evaluation Function Based on the Principle of Maximum Likelihood Estimation Becomes the Maximum Likelihood Value The horizontal direction array maximum likelihood candidate extraction unit 301 is a local maximum value (maximum ^{_{value) E subH (θ (1)}} , θ (2), ..., θ (NW)) angle ^(θ _NHLocalML ⁽¹⁾ to _{^{give, θ NHLocalML (2), ...}} , to extract θ _NHLocalML ^(NW)).
E _subH (θ ⁽¹⁾ , θ ⁽²⁾ _, ..., θ ^(NW) )> α _H × E _HML (22)

However, it is NHLocalML = 1, ..., N _HLM . Also, E _HML is the maximum value (maximum likelihood value) [θ _ML ⁽¹⁾ of evaluation functions E _SubH (θ ⁽¹⁾ , θ ⁽²⁾ _, ..., θ ^(NW) ) in a predetermined search grid in the horizontal direction , θ _ML ⁽²⁾ _, ..., θ _ML ^(NW) ]. Further, α _H is a predetermined value (α _H <1). That is, the following equation (23) is satisfied.
E _HML = E _{sub H} (θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ _, ..., θ _ML ^(NW) ) (23)

In addition, when the local maximum value which satisfy _{| fills the} condition shown to Formula (22) exceeds predetermined number _NH (N _HLM > N _H ), horizontal direction array maximum likelihood candidate extraction part 301, evaluation function E _SubH ((theta ^{) (1)} , θ ⁽²⁾ _, ..., θ ^(NW) may be output with priority given to those with larger values of _NH or smaller.

<Operation of Vertical Direction Array Maximum Likelihood Candidate Extraction Unit 302>
The vertical array maximum likelihood candidate extraction unit 302 performs the following processing based on the virtual reception array correlation vector _{h_after_cal} (k, fs, w) obtained by correcting the inter-antenna deviation, which is input from the inter-antenna deviation correction unit 241. .

Specifically, first, the vertical array maximum likelihood candidate extraction unit 302 _calculates the virtual reception antennas VA # 1,..., _Which are included in the virtual reception array correlation vector _{h_after_cal} (k, fs, w) in which the deviation between antennas is corrected. , VA # (Nt × Na), vertical array correlation vector h _SubV (composed of vertical linear array elements constituting a linear array of three or more antennas in the vertical direction on the virtual reception array) Extract k, fs, w).

Then, the vertical direction array maximum likelihood candidate extraction unit 302 performs maximum likelihood estimation processing in the vertical direction using the extracted vertical direction array correlation vector h _SubV (k, fs, w). In the vertical maximum likelihood estimation, the vertical array maximum likelihood candidate extraction unit 302 determines a predetermined evaluation function E _SubV (φ ⁽¹⁾ , φ ⁽ _m ⁾ based on the principle of maximum likelihood estimation within a predetermined vertical search grid. ²⁾ Calculate the angle (maximum likelihood value) at which the _, ..., φ ^(NW) ) becomes minimum or maximum. In the variation 1, the vertical array maximum likelihood candidate extraction unit 302 adds to the maximum likelihood value (corresponding to NW angles) and at least one other than the maximum likelihood value of the evaluation function used for the maximum likelihood estimation process in the vertical direction. One local maximum likelihood value (extreme value) (each corresponding to NW angles) is extracted. Then, the vertical direction array maximum likelihood candidate extraction unit 302 determines each of NW angles corresponding to the maximum likelihood value and at least one local maximum likelihood value (extreme value) other than the maximum likelihood value in the evaluation function. The arrival angle candidate (maximum likelihood candidate) in the vertical direction including NW angles is output to the horizontal / vertical maximum likelihood estimation unit 303.

  The angle that is the local maximum likelihood value is, for example, a value that satisfies the following condition.

1) When the Minimum Value of a Predetermined Evaluation Function Based on the Principle of Maximum Likelihood Estimation Becomes the Maximum Likelihood Value The vertical direction array maximum likelihood candidate extraction unit 302 determines the local minimum value (minimum value) that satisfies Value) _Extract an angle (φ _NVLocalML ⁽¹⁾ , φ _NVLocalML ⁽²⁾ _, ..., Φ _NVLocalML ^(NW) ) giving E _subV (φ ⁽¹⁾ , φ ⁽²⁾ _, ..., φ ^(NW) ).
E _subV (φ ⁽¹⁾ , φ ⁽²⁾ _, ..., φ ^(NW) ) <α _V × E _VML (24)

However, NVLocalML = 1, ..., a N _VLM. Also, E _VML is the minimum value of evaluation functions E _SubV (φ ⁽¹⁾ , φ ⁽²⁾ _, ..., φ ^(NW) ) in a predetermined search grid in the vertical direction [φ _ML ⁽¹⁾ , φ _ML ^{(2 _),} ..., it is a φ _ML ^(NW)]. Moreover, (alpha) _V is a predetermined value ((alpha) _V > 1). That is, the following equation (25) is satisfied.
E _VML = E _{sub V} (φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ _, ..., φ _ML ^(NW) ) (25)

When the local minimum value satisfying the condition shown in equation (24) exceeds the predetermined number N _V (N _VLM > N _V ), the vertical direction array maximum likelihood candidate extraction unit 302 evaluates the evaluation function E _SubV (φ ^{(1) _{, φ (2), ...,}} φ (NW)) to the smaller value may output N _V following candidates and priority.

2) When the Maximum Value of the Predetermined Evaluation Function Based on the Principle of Maximum Likelihood Estimation Becomes the Maximum Likelihood Value The vertical direction array maximum likelihood candidate extraction unit 302 determines the local maximum value (maximum Value) _Extract an angle (φ _NVLocalML ⁽¹⁾ , φ _NVLocalML ⁽²⁾ _, ..., Φ _NVLocalML ^(NW) ) giving E _subV (φ ⁽¹⁾ , φ ⁽²⁾ _, ..., φ ^(NW) ).
E _subV (φ ⁽¹⁾ , φ ⁽²⁾ _, ..., φ ^(NW) )> α _H × E _VML (26)

However, NVLocalML = 1, ..., a N _VLM. Also, E _VML is the maximum value (maximum likelihood value) [φ _ML ⁽¹⁾ of evaluation functions E _SubV (φ ⁽¹⁾ , φ ⁽²⁾ _, ..., φ ^(NW) ) in a predetermined search grid in the vertical direction , φ _ML ⁽²⁾ _, ..., φ _ML ^(NW) ]. Further, α _V is a predetermined value (α _V <1). That is, the following equation (27) is satisfied.
E _VML = E _{sub V} (φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ _, ..., φ _ML ^(NW) ) (27)

When the local minimum value satisfying the condition shown in equation (26) exceeds the predetermined number N _V (N _VLM > N _V ), the vertical direction array maximum likelihood candidate extraction unit 302 evaluates the evaluation function E _SubV (φ ^{(1) _{, φ (2), ...,}} φ (NW)) towards the larger value may output N _V following candidates and priority.

<Operation of Horizontal / Vertical Maximum Likelihood Estimator 303>
The horizontal / vertical maximum likelihood estimation unit 303 outputs the result of the angle that is the maximum likelihood candidate (horizontal arrival angle candidate) within the horizontal search grid, which is input from the horizontal array maximum likelihood candidate extraction unit 301 [ θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ _, ..., θ _ML ^(NW) ] and [θ _NHLocalML ⁽¹⁾ , θ _NHLocalML ⁽²⁾ _, ..., θ _NHLocalML ^(NW) ] (NHLocalML = 1, ..., N _HLM ) and the output result of the angle that is the maximum likelihood candidate (vertical arrival angle candidate) in the vertical search grid, which is input from the vertical array maximum likelihood candidate extraction unit 302 [φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ _, ..., φ _ML ^(NW) ] and [φ _NVLocalML ⁽¹⁾ , φ _NVLocalML ⁽²⁾ _, ..., φ _NVLocalML ^(NW) ] (NVLocalML = 1, ..., N _VLM ) (Θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., θ ^(NW) , φ ^(NW)) of the arrival angles of NW arrival waves in a two-dimensional plane extending in the direction and the vertical direction Estimate).

  Specifically, the horizontal / vertical maximum likelihood estimation unit 303 searches a combination of an arrival angle candidate corresponding to the horizontal maximum likelihood value and an arrival angle candidate corresponding to the vertical maximum likelihood value as a search angle candidate. A two-dimensional maximum likelihood estimation process in the horizontal direction and vertical direction with a limited grid is performed.

  The details of the horizontal and vertical two-dimensional maximum likelihood estimation processing in the horizontal / vertical maximum likelihood estimation unit 303 will be described below.

The horizontal / vertical maximum likelihood estimation unit 303 determines angles [θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ _, ..., Θ _ML ^(NW) ] and [θ _NHLocalML ⁽¹⁾ , θ that are the maximum likelihood candidates in the horizontal direction. ^{_{NHLocalML (2), ..., θ}} NHLocalML (NW)] (NHLocalML = 1, ..., N HLM) taking out one of the most likely candidates from among the. Also, the horizontal / vertical maximum likelihood estimation unit 303 determines angles [φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ _, ..., Φ _ML ^(NW) ] and [φ _NVLocalML ^{(1) which} are maximum likelihood candidates in the vertical direction. ^{_{, φ NVLocalML (2), ...}} , φ NVLocalML (NW)] (NVLocalML = 1, ..., N VLM) taking out one of the most likely candidates from among the. Then, the horizontal / vertical maximum likelihood estimation unit 303 determines two-dimensional (NW × NW) grid points in the horizontal direction and the vertical direction based on the maximum likelihood candidate extracted in each of the horizontal direction and the vertical direction. Then, search of NW different combinations (two-dimensional maximum likelihood estimation processing) is performed. Therefore, _{(Nw × Nw)} C _Nw combinations of θ and φ become the number of searches of the two-dimensional maximum likelihood estimation in the horizontal direction and the vertical direction.

In horizontal and vertical two-dimensional maximum likelihood estimation, the horizontal / vertical maximum likelihood estimation unit 303 uses the virtual reception array correlation vector _{h_after_cal} (k, fs, w) corrected for the inter-antenna deviation to The predetermined evaluation function E _ML2D (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., θ ^(NW) , φ ^(NW) ) based on the principle of likelihood estimation is the minimum or maximum The angles (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., Θ ^(NW) , φ ^(NW) ) are extracted. Also, the horizontal / vertical maximum likelihood estimation unit 303 temporarily stores the extracted angle and the evaluation function value corresponding to the angle.

Then, the horizontal / vertical direction maximum likelihood estimator 303, the angle [θ _ML ⁽¹⁾ of the two-dimensional maximum likelihood estimation of the same in the horizontal and vertical directions, the horizontal direction of the maximum likelihood candidate, theta _ML ^{( 2)} _, ..., θ _ML ^(NW) ] and [θ _NHLocalML ⁽¹⁾ , θ _NHLocalML ⁽²⁾ _, ..., θ _NHLocalML ^(NW) ] (NHLocalML = 1, ..., N _HLM ) and other maximum likelihood Take out a candidate. Also, the horizontal / vertical maximum likelihood estimation unit 303 determines angles [φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ _, ..., Φ _ML ^(NW) ] and [φ _NVLocalML ^{(1) which} are maximum likelihood candidates in the vertical direction. ^{_{, φ NVLocalML (2), ...}} , φ NVLocalML (NW)] (NVLocalML = 1, ..., N VLM) retrieve other maximum likelihood candidates of. Then, the horizontal / vertical maximum likelihood estimation unit 303 determines two-dimensional (NW × NW) grid points in the horizontal direction and the vertical direction based on the maximum likelihood candidate extracted in each of the horizontal direction and the vertical direction. Then, search of NW different combinations (two-dimensional maximum likelihood estimation processing) is performed.

  When the horizontal / vertical maximum likelihood estimation unit 303 uses an evaluation function whose minimum value is the maximum likelihood value, the evaluation function value corresponding to the extracted angle is smaller than the temporarily stored evaluation function value. In this case, the temporarily stored content is updated using the evaluation function value and the corresponding angle (maximum likelihood value). When the horizontal / vertical maximum likelihood estimation unit 303 uses an evaluation function whose maximum value is the maximum likelihood value, the evaluation function value corresponding to the extracted angle is calculated from the evaluation function value temporarily stored. Update the content to be stored temporarily if too large.

Thus, the horizontal / vertical maximum likelihood estimation unit 303 extracts the maximum likelihood candidate, estimates the maximum likelihood, and updates the temporarily stored content (evaluation function value and angle) in the horizontal and vertical directions. It is performed on all combinations of maximum likelihood candidates of directions. Here, all combinations in the horizontal direction and the vertical direction are (N _HLM +1) × (N _VLM +1).

Thus, the angle temporarily stored when the search for all the combinations of maximum likelihood candidates is completed is a predetermined evaluation function E _ML2D (θ ⁽ θ ^(a)) based on the principle of maximum likelihood estimation among the combinations of searched angles. ¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ _, ..., Θ ^(NW) , φ ^(NW) ) becomes an angle which becomes minimum or maximum. The horizontal / vertical maximum likelihood estimation unit 303 outputs the angle as a two-dimensional arrival direction estimated value in the horizontal direction and the vertical direction.

  Thus, the horizontal / vertical maximum likelihood estimation unit 303 determines the arrival angles of NW arrival waves in a two-dimensional plane from combinations of horizontal arrival angle candidates and vertical arrival angle candidates. .

  As an example, the case of the number of incoming waves NW = 2 will be described.

In the case of the arrival wave number NW = 2, the horizontal maximum likelihood candidates θ ⁽¹⁾ and θ ⁽²⁾ and the vertical maximum likelihood candidates φ ⁽¹⁾ and φ ⁽²⁾ as another combination of maximum likelihood candidates. Since is extracted, all combinations for searching two different grid points from four grid points are six (= ₄ C ₂ ) as in FIG.

For example, the maximum likelihood values θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ in the horizontal direction and the maximum likelihood values φ _ML ⁽¹⁾ , φ _ML ^{(2) in} the vertical direction are extracted as a combination of maximum likelihood candidates. In this case, the horizontal / vertical maximum likelihood estimation unit 303 estimates the maximum likelihood among the combinations of the searched angles using the virtual reception array correlation vector _{h_after_cal} (k, fs, w) in which the inter-antenna deviation is corrected. The predetermined evaluation function E _ML2D (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ ) based on the principle of the minimum (if the minimum is the maximum likelihood value) or the maximum (the maximum is the maximum The angle (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ ) to be the case of the likelihood value is calculated. Then, the horizontal / vertical maximum likelihood estimation unit 303 temporarily stores the extracted angle and the corresponding evaluation function value.

Next, as another combination of maximum likelihood candidates, for example, maximum likelihood values θ _ML ⁽¹⁾ , θ _ML ⁽²⁾ in the horizontal direction, and an angle [φ _NVLocalML ^{(1 ),} if φ _NVLocalML ^(2)] is taken out, horizontal / vertical maximum likelihood estimator 303, the virtual reception array correlation vector _h _after_cal (k obtained by correcting the inter-antenna difference, fs, w) using Among the combinations of the searched angles, a predetermined evaluation function E _ML2D (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ ) based on the principle of maximum likelihood estimation is calculated. Then, when using the evaluation function in which the minimum value is the maximum likelihood value, the horizontal / vertical maximum likelihood estimation unit 303 calculates the calculated evaluation function value if it is smaller than the temporarily stored evaluation function value. The temporarily stored content is updated using the evaluation function value and the corresponding angle. Note that the horizontal / vertical maximum likelihood estimation unit 303 temporarily uses the evaluation function whose maximum value is the maximum likelihood, and the calculated evaluation function value is temporarily larger than the temporarily stored evaluation function value. Update the contents stored in.

Also, as another combination of maximum likelihood candidates, the angle [θ _NHLocalML ⁽¹⁾ , θ _NHLocalML ⁽²⁾ ] at which the extremum is located in the horizontal search grid, and the maximum likelihood value in the vertical search grid When the angles [φ _ML ⁽¹⁾ , φ _ML ⁽²⁾ ] are extracted, the horizontal / vertical maximum likelihood estimation unit 303 estimates the virtual reception array correlation vector _{h_after_cal} (k, with the antenna deviation corrected). A predetermined evaluation function E _{ML 2 D} (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ ) based on the principle of maximum likelihood estimation among combinations of angles searched using fs, w) Calculate Then, when the calculated evaluation function value is smaller (or larger) than the temporarily stored evaluation function value, the horizontal / vertical maximum likelihood estimation unit 303 uses the calculated evaluation function value and the corresponding angle. Update the temporarily stored content.

Also, as another combination of maximum likelihood candidates, angles [θ _NHLocalML ⁽¹⁾ , θ _NHLocalML ⁽²⁾ ] at which extrema are located in the horizontal search grid, and extrema in the vertical search grid When the angle [φ _NVLocalML ⁽¹⁾ , φ _NVLocalML ⁽²⁾ ] is extracted, the horizontal / vertical maximum likelihood estimation unit 303 corrects the inter-antenna deviation, and the virtual reception array correlation vector _{h_after_cal} (k, fs) and w) are used to calculate a predetermined evaluation function E _ML2D (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ ) based on the principle of maximum likelihood estimation among combinations of searched angles. calculate. Then, when the calculated evaluation function value is smaller (or larger) than the temporarily stored evaluation function value, the horizontal / vertical maximum likelihood estimation unit 303 uses the calculated evaluation function value and the corresponding angle. Update the temporarily stored content.

All combinations of horizontal and vertical maximum likelihood candidates are (N _HLM +1) × (N _VLM +1). The horizontal / vertical maximum likelihood estimation unit 303 similarly determines a predetermined evaluation function E _ML2D (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ^{(2 )} based on the principle of maximum likelihood estimation for all combinations of maximum likelihood candidates. _^), phi ⁽²⁾⁾ is calculated, if the calculated evaluation function value is smaller than the evaluation function value which is temporarily stored (or large), and calculated evaluation function value, temporarily using the corresponding angle Update the contents to be stored.

The angle temporarily stored when the search of the search range for all combinations of maximum likelihood candidates is finished is a predetermined evaluation function E _ML2D (θ that is based on the principle of maximum likelihood estimation among the combinations of the searched angles. ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ ) is an angle at which the minimum (if the minimum value is the maximum likelihood value) or the maximum (when the maximum value is the maximum likelihood value). The horizontal / vertical maximum likelihood estimation unit 303 outputs the angle as a two-dimensional estimated value of the direction of arrival (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ ) in the horizontal and vertical directions. Do. Also, the horizontal / vertical maximum likelihood estimation unit 303 may output the discrete time k and the Doppler frequency fsΔΦ at that time together with the calculated estimated value of the arrival angle as the arrival direction estimation result.

  The operation of the direction estimation unit 214 according to the variation 1 has been described above.

  As described above, in the variation 1, the direction estimation unit 214 determines the horizontal and vertical maximum likelihood values extracted by the horizontal direction array maximum likelihood candidate extraction unit 301 and the vertical direction array maximum likelihood candidate extraction unit 302, respectively. In addition to the above angles, two-dimensional maximum likelihood estimation processing in the horizontal direction and vertical direction is performed using a plurality of angle candidates (maximum likelihood candidates) including extreme values.

  For example, when the angular intervals in the search grid are set relatively coarsely, the extremum may be erroneously set as the maximum likelihood value. On the other hand, in the variation 1, the direction estimation unit 214 satisfies a predetermined condition (for example, equations (20), (22), (24), (26), etc.) in addition to the maximum likelihood value in the search grid. Include the extrema as the maximum likelihood candidate (angle candidate). Thus, the direction estimation unit 214 performs two-dimensional maximum likelihood estimation processing in the horizontal direction and the vertical direction using the combination of the maximum likelihood candidates obtained by the maximum likelihood estimation processing in the horizontal direction and the vertical direction. By doing this, it is possible to increase the probability that the maximum likelihood candidate (that is, the correct maximum likelihood value) having the smallest or largest evaluation function value can be obtained.

  Therefore, according to the variation 1, it is possible to improve the estimation accuracy of the arrival angle by the two-dimensional maximum likelihood estimation in the horizontal direction and the vertical direction.

In the variation 1, the total number of searches in the horizontal direction array maximum likelihood candidate estimation unit 301 and the vertical direction array maximum likelihood candidate estimation unit 302 is ( _(NGH) C _NW + _(NGV) C _NW ) times. Furthermore, the horizontal / vertical maximum likelihood estimation unit 303 limits the search range to the angular range to which the horizontal array maximum likelihood estimation unit 301 and the vertical array maximum likelihood estimation unit 302 are output. The upper limit value of the number of searches in the estimation unit 303 is (N _H +1) × (N _V +1) × _{(Nw × Nw)} C _Nw .

For example, even if (N _H +1) × (N _V +1) is approximately 10 to 20, the horizontal direction array maximum likelihood candidate estimation unit 301 and the vertical direction array maximum likelihood candidate can be obtained for all the number of searches of the direction estimation unit 214 The number of times of the search in the estimation unit 302 ( _(NGV) C _NW + _(NGH) C _NW ) takes a larger proportion. That is, in all the number of searches of the direction estimation unit 214, the influence of the increase in the number of searches due to the addition of extreme values other than the maximum likelihood value as the maximum likelihood is small. Therefore, according to the variation 1, as in the above embodiment, the number of searches can be significantly reduced as compared with the conventional method, and the estimation accuracy of the arrival angle by the two-dimensional maximum likelihood estimation can be improved.

(Variation 2 of Embodiment)
At the time of maximum likelihood estimation with respect to a two-dimensional plane in the direction estimation unit 214 (see FIG. 6 or FIG. 11), the horizontal / vertical maximum likelihood estimation units 244 and 303 calculate maximum likelihood in one dimension (horizontal direction or vertical direction). With the value as an initial value, the steepest-gradient method may be used to estimate the arrival angle in a two-dimensional plane of the incoming wave while narrowing the angular grid spacing.

  As a result, as in the above-described embodiment and variation 1, the direction estimation unit 214 can suppress an increase in the amount of computation and improve the estimation accuracy of the arrival angle.

  Note that as another configuration of the direction estimation unit 214, the direction estimation unit 214 sets the search grid interval to the initial value using the output of the horizontal / vertical maximum likelihood estimation unit 244 or 303 (see FIG. 6 or 11). A horizontal / vertical local search unit 401 may be provided to narrow the local search. FIG. 12 is a block diagram showing a configuration example of the direction estimation unit 214 in which the horizontal / vertical direction local search unit 401 is added to the configuration of the above embodiment (FIG. 6). FIG. 13 is a block diagram showing a configuration example of the direction estimation unit 214 in which the horizontal / vertical direction local search unit 401 is added to the configuration of the variation 1 (FIG. 11).

  In the horizontal / vertical local search unit 401, local search is performed with the outputs of the horizontal / vertical maximum likelihood estimation units 244 and 303 as initial values, thereby suppressing an increase in the amount of computation as in the above embodiment and variation 1. While, it is possible to improve the estimation accuracy of the arrival angle.

Also, the horizontal / vertical maximum likelihood estimation units 244 and 303 output, as an output to the horizontal / vertical direction local search unit 401, a predetermined evaluation function E _ML2D (based on the principle of maximum likelihood estimation) among combinations of the searched angles. In addition to the angle at which θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, φ ⁽²⁾ ) become the minimum or maximum, the evaluation function E _ML2D (θ ⁽¹⁾ , φ ⁽¹⁾ , θ ⁽²⁾ _, A plurality of angle candidates may be output such that φ ⁽²⁾ is the next minimum value (second minimum) or the second maximum value (second maxiimum).

  In this case, the horizontal / vertical local search unit 401 performs a local search with each of the plurality of angle candidates input from the horizontal / vertical maximum likelihood estimation units 244 and 303 as initial values, and as local search results for each angle candidate. The minimum or maximum angle among the obtained evaluation function values may be output as an estimated value of the two-dimensional arrival angle in the horizontal direction and the vertical direction.

  As a result, depending on the angular interval in the search grid, the extremum may be erroneously made the maximum likelihood value. On the other hand, since the horizontal / vertical local search unit 401 can perform local search by making the search grid more finely for a plurality of angle candidates, it is possible to increase the probability that the correct maximum likelihood value can be obtained. it can. Therefore, the estimation accuracy of the arrival angle by the horizontal and vertical two-dimensional maximum likelihood estimation can be enhanced.

  Alternatively, as the local search method, the Alternating Projection method described in Non-Patent Document 1, the EM method or SAGE method described in Non-Patent Document 3 may be applied, or other methods may be applied.

(Variation 3)
Variation 3 uses an arrangement in which the horizontal and vertical array apertures of the virtual receive array are maximally expanded when applying MIMO radar. As an arrangement in which the horizontal and vertical array apertures of the virtual reception array are maximally expanded, for example, the transmission and reception arrays (the transmission antenna 106 and the reception antenna 202) may be arranged in an L shape or a T shape. The arrangement of the transmission / reception array is not limited to the L-shape and the T-shape.

  Thereby, the angular resolution in the radar device 10 can be further enhanced.

  As an example, FIG. 14A illustrates an example of an array antenna configuration of a radar device (MIMO radar) according to Variation 3.

  In FIG. 14A, the number Nt of transmission antennas 106 is four, and the number Na of reception antennas 202 is four. Also, four transmit antennas 106 are represented by Tx # 1 to Tx # 4, and four receive antennas 202 are represented by Rx # 1 to Rx # 4. FIG. 14B also shows the arrangement of virtual reception arrays obtained by the antenna arrangement shown in FIG. 14A.

  In FIG. 14A, in the transmitting array antenna, four antennas are arranged in a shape in which the L-shape is inverted upside down, and in the receiving array antenna, four antennas are arranged in a shape in which the L-shape is horizontally inverted. In this case, a virtual reception array arrangement consisting of 16 antennas (VA # 1 to VA # 16) shown in FIG. 14B is obtained.

In the virtual reception array shown in FIG. 14B, the antenna aperture lengths D _H and D _{V in} the horizontal and vertical directions are D _H = 5 d _H and D _V = 5 d _V , respectively. Here, d _H is the element spacing in the horizontal direction of the transmitting array antenna, and d _V is the element spacing in the vertical direction of the transmitting array antenna.

In the case of FIG. 14B, the horizontal array maximum likelihood estimation unit 242 shown in FIG. 6 (or the horizontal array maximum likelihood candidate extraction unit 301 shown in FIG. 11) has horizontal array correlation vectors {N _VAH = 6, 3 and 3 { h _{SubH (1)} (k, fs, w), h _{SubH (2)} (k, fs, w), h _{SubH (3)} (k, fs, w)} (that is, N _subH = 3 virtual horizontal _lines ) Directional linear arrays can be used. The element numbers of virtual reception array correlation vector _{h_after_cal} (k, fs, w) included in each horizontal array correlation vector are {VA # 5, VA # 6, VA # 9, VA # 10, VA # 13, VA, respectively. # 14}, {VA # 7, VA # 11, VA # 15}, {VA # 8, VA # 12, VA # 16}.

Also, corresponding to horizontal array correlation vector {h _{SubH (1)} (k, fs, w), h _{SubH (2)} (k, fs, w), h _{SubH (3)} (k, fs, w)} The horizontal array direction vector {a _{SubH (1)} (θ _u , α), a _{Sub H (2)} (θ _u , α), a _{Sub H (3)} (θ _u , α)} is the direction vector of the virtual reception array Element numbers of a (θ _u , φ _v ) {VA # 5, VA # 6, VA # 9, VA # 10, VA # 13, VA # 14}, {VA # 7, VA # 11, VA # 15} , {VA # 8, VA # 12, VA # 16} are respectively extracted and configured column vectors.

Note that the horizontal array maximum likelihood estimation unit 242 (or the horizontal array maximum likelihood candidate extraction unit 301) selects only the horizontal array correlation vector with the longest aperture length as the horizontal array correlation vector used for maximum likelihood estimation processing. You may use it. For example, in the case of FIG. 14B, the horizontal array correlation vector h _{SubH (1)} (k, fs, w) of N _VAH = 6 is used as the horizontal array correlation vector with the longest aperture length. As a result, the amount of calculation of the evaluation function value can be reduced.

Further, in the case of FIG. 14B, (vertical array maximum likelihood candidate extraction unit 302 shown in or Fig. 11) vertical array maximum likelihood estimator 243 shown in FIG. 6, the vertical array correlation N _VAV = 6,3,3 Vectors {h _{SubV (1)} (k, fs, w), h _{SubV (2)} (k, fs, w), h _{SubV (3)} (k, fs, w)} (that is, N _subV = 3 A virtual vertical linear array can be used. The element numbers of the virtual reception array correlation vector _{h_after_cal} (k, fs, w) included in each vertical array correlation vector are {VA # 2, VA # 3, VA # 4, VA # 6, VA # 7, VA, respectively. # 8, {VA # 10, VA # 11, VA # 12}, {VA # 14, VA # 15, VA # 16}.

Also, it corresponds to vertical array correlation vector {h _{SubV (1)} (k, fs, w), h _{SubV (2)} (k, fs, w), h _{SubV (3)} (k, fs, w)} vertical array direction vector _{{a SubV (1) (α} SV, φ ν), a SubV (2) (α SV, φ ν), a SubV (3) (α SV, φ ν)} , the virtual reception array Element number {VA # 2, VA # 3, VA # 4, VA # 6, VA # 7, VA # 8}, {VA # 10, VA # 11, VA of the direction vector a (θ _u , φ _v ) of It is a column vector configured by respectively extracting # 12, {VA # 14, VA # 15, VA # 16}.

Note that the vertical array maximum likelihood estimation unit 243 (or the vertical array maximum likelihood candidate extraction unit 302) selects only the vertical array correlation vector with the longest aperture length as the vertical array correlation vector used for the maximum likelihood estimation process. You may use it. For example, in the case of FIG. 14B, most aperture length is long vertical array correlation vector, N vertical array correlation vector h _{SubV (1)} of the _{VAV = 6 (k, fs,} w) is used. Thus, the effect of reducing the amount of calculation of the evaluation function value can be obtained.

Here, the transmission / reception array antenna (FIG. 14A) according to the variation 3 and the transmission / reception antenna shown in FIG. 1A are both configured by four transmission antennas and four reception antennas. In the virtual receiver array shown in FIG. 1B, the horizontal and vertical aperture lengths are 3d _H and 3d _V , respectively. On the other hand, as shown in FIG. 14B, in the variation 3, the horizontal and vertical opening lengths are 5 d _H and 5 d _V , respectively. That is, in the variation 3, the aperture length in the virtual reception array can be increased although it is configured by the same number of transmission / reception antennas as compared with FIG. 1B.

As in the variation 3, by using an arrangement based on an L-shape (see FIG. 14A) or a T-shape (not shown), the transmit and receive array antennas can be used for horizontal array correlation vectors or vertical array correlation vectors. The number of elements (N _VAH or N _VAV ) can be maximized to maximize the aperture length of the virtual horizontal linear array or virtual vertical array. This can improve the estimation accuracy of the arrival angle in the horizontal or vertical direction.

  The embodiments according to one aspect of the present disclosure have been described above.

  In addition, you may implement combining the operation | movement which concerns on the said embodiment and each variation suitably.

Other Embodiments
(1) The number Nt of transmitting antennas is not limited to the three elements shown in FIG. 7A or the four elements shown in FIG. 14A, and the number Na of receiving antennas is not limited to the three elements shown in FIG. 7A or the four elements shown in FIG. Further, the present disclosure is not limited to the transmission / reception array antenna arrangement (virtual reception array arrangement) shown in FIGS. 7A, 7B, 14A and 14B, and is a two-dimensionally arranged virtual reception array in the horizontal and vertical directions. Applicable to

  (2) In the above embodiment, the case of using the coded pulse radar has been described, but the present disclosure is also applicable to a radar system using a frequency modulated pulse wave such as a Chirp pulse radar. .

  (3) In the above embodiment, as an example, the case of performing the arrival direction estimation using a virtual reception array determined by the arrangement of transmission / reception array antennas of the MIMO radar has been described, but the present disclosure is not limited thereto The present invention is also applicable to the case of performing arrival direction estimation using a single transmitting antenna and a plurality of receiving array antennas arranged two-dimensionally in the horizontal direction and the vertical direction.

  (4) In the radar device 10 shown in FIG. 2, the radar transmission unit 100 and the radar reception unit 200 may be individually disposed at physically separated places. Further, in the radar receiver 200 shown in FIG. 2, the direction estimation unit 214 (arrival direction estimation device) and the other components may be separately disposed at physically separated places.

  (5) Although not shown, the radar apparatus 10 includes, for example, a central processing unit (CPU), a storage medium such as a ROM (Read Only Memory) storing a control program, and a working memory such as a RAM (Random Access Memory). Have. In this case, the functions of the above-described units are realized by the CPU executing a control program. However, the hardware configuration of the radar device 10 is not limited to such an example. For example, each functional unit of the radar device 10 may be realized as an integrated circuit (IC) that is an integrated circuit. Each functional unit may be individually integrated into a single chip, or may be integrated into a single chip so as to include part or all thereof.

  Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is apparent that those skilled in the art can conceive of various modifications or alterations within the scope described in the claims, and they are naturally within the technical scope of the present disclosure. It is understood. In addition, the components in the above-described embodiment may be arbitrarily combined without departing from the scope of the disclosure.

  In the above embodiments, the present disclosure has been described as an example configured using hardware, but the present disclosure can also be realized with software in cooperation with hardware.

  Further, each functional block employed in the description of each of the above-described embodiments may typically be implemented as an LSI constituted by an integrated circuit. The integrated circuit may control each functional block used in the description of the above embodiment and may include an input terminal and an output terminal. These may be individually made into one chip, or may be made into one chip so as to include some or all. Although an LSI is used here, it may be called an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. After the LSI is manufactured, an FPGA (field programmable gate array) that can be programmed, or a reconfigurable processor that can reconfigure connection or setting of circuit cells in the LSI may be used.

  Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to integrate functional blocks using this technology. The application of biotechnology etc. may be possible.

<Summary of this disclosure>
A radar device according to the present disclosure includes: a transmitting unit that transmits a radar signal using a transmitting array antenna; a receiving unit that receives a reflected wave signal in which the radar signal is reflected by a target using a receiving array antenna; A direction estimation unit for estimating an arrival angle of the reflected wave signal, and the direction estimation unit is included in a virtual reception array configured based on the arrangement of the transmission array antenna and the reception array antenna Maximum likelihood estimation process for the first direction by using the reception signal of the first virtual straight line array configured by the virtual reception antennas linearly arranged in the first direction among the plurality of virtual reception antennas Calculates a first maximum likelihood value corresponding to NW (NW is an integer of 1 or more) angles in the first direction, and the first direction including at least the first maximum likelihood value A first estimation unit for extracting a first arrival angle candidate of an incoming wave in a direction, and a virtual arrangement linearly arranged in a second direction orthogonal to the first direction among the plurality of virtual reception antennas A second maximum likelihood value corresponding to the NW angles in the second direction by maximum likelihood estimation processing for the second direction using a received signal of the second virtual linear array configured by the receiving antenna. A second estimation unit for calculating a second arrival angle candidate of the arrival wave in the second direction including at least the second maximum likelihood value, and calculating the first arrival angle candidate and the second And a third estimation unit configured to estimate angles of arrival of the NW arrival waves in a two-dimensional plane extending in the first direction and the second direction using the arrival angle candidate of

  In the radar device of the present disclosure, the third estimation unit may be a combination of the NW angles corresponding to the first maximum likelihood value and the NW angles corresponding to the second maximum likelihood value. Among them, the arrival angles of the NW arrival waves in the two-dimensional plane are determined.

  In the radar device of the present disclosure, the first estimation unit may determine the NW angles corresponding to the first maximum likelihood value, and the first estimation function used in the maximum likelihood estimation process. The first arrival angle candidate including the NW angles corresponding to at least one extreme value other than the maximum likelihood value of 1 is extracted, and the second estimation unit corresponds to the second maximum likelihood value. And the NW angles corresponding to at least one extreme value other than the second maximum likelihood value in the second evaluation function used in the maximum likelihood estimation process. The second estimation unit extracts two arrival angle candidates, and the third estimation unit extracts the NW arriving waves in the two-dimensional plane from among the combinations of the first arrival angle candidate and the second arrival angle candidate. Determine the arrival angle of

  In the radar device of the present disclosure, the third estimation unit performs maximum likelihood estimation processing on a two-dimensional plane with respect to a combination of the first arrival angle candidate and the second arrival angle candidate, The arrival angles of the NW arrival waves in a plane are estimated.

  In the radar device according to the present disclosure, the third estimation unit may use the NW number of in the two-dimensional plane according to the steepest gradient method having the first arrival angle candidate and the second arrival angle candidate as initial values. Estimate the arrival angle of the incoming wave.

  In the radar apparatus according to the present disclosure, in the maximum likelihood estimation process, an evaluation function including a reception signal of the virtual reception antenna and a direction vector of the virtual reception antenna is used, and among parameters used for the evaluation function, Parameters related to the direction vector are stored in advance.

  An arrival direction estimation apparatus according to the present disclosure is an arrival direction estimation apparatus that estimates an arrival angle of a received signal using a plurality of receiving antennas, and is linear in a first direction among the plurality of receiving antennas. Using the received signal of the first linear array configured by the receiving antennas arranged in the first to the NWs in the first direction (NW is an integer of 1 or more) by maximum likelihood estimation processing for the first direction. A first estimation unit which calculates a first maximum likelihood value corresponding to an angle, and extracts a first arrival angle candidate of an incoming wave in the first direction including at least the first maximum likelihood value; Using a reception signal of a second linear array composed of reception antennas linearly arranged in a second direction orthogonal to the first direction among a plurality of reception antennas, using a reception signal in the second direction According to the maximum likelihood estimation process, the second Calculating a second maximum likelihood value corresponding to the NW angles in the second direction, and extracting a second arrival angle candidate of the incoming wave in the second direction including at least the second maximum likelihood value; And the arrival angles of the NW arrival waves in a two-dimensional plane extending in the first direction and the second direction using the first arrival angle candidate and the second arrival angle candidate. And a third estimation unit for estimating

  The present disclosure is suitable as a radar device that detects a wide-angle range.

Reference Signs List 10 radar apparatus 100 radar transmission unit 200 radar reception unit 300 reference signal generation unit 101, 101a radar transmission signal generation unit 102 code generation unit 103 modulation unit 104 LPF
105 transmit wireless unit 106 transmit antenna 111 code storage unit 112 DA conversion unit 201 antenna system processing unit 202 receive antenna 203 receive wireless unit 204 amplifier 205 frequency converter 206 orthogonal detector 207 signal processing unit 208, 209 AD conversion unit 210 separation unit 211 correlation operation unit 212 addition unit 213 Doppler frequency analysis unit 214 direction estimation unit 241 inter-antenna deviation correction unit 242 horizontal array maximum likelihood estimation unit 243 vertical array maximum likelihood estimation unit 244, 303 horizontal / vertical maximum likelihood estimation unit 301 Horizontal direction array maximum likelihood candidate extraction unit 302 Vertical direction array maximum likelihood candidate extraction unit 401 Horizontal / vertical direction local search unit

Claims (7)

A transmitting unit that transmits a radar signal using a transmitting array antenna;
A receiving unit for receiving a reflected wave signal in which the radar signal is reflected at a target using a receiving array antenna;
A direction estimation unit for estimating an arrival angle of the received reflected wave signal;
Equipped with
The direction estimation unit
A plurality of virtual reception antennas included in a virtual reception array configured based on the arrangement of the transmission array antenna and the reception array antenna, the virtual reception antenna being linearly arranged in a first direction; First received the signals of the first imaginary straight line array, the first maximum corresponding to NW (NW is an integer of 1 or more) angles in the first direction by maximum likelihood estimation processing for the first direction. A first estimation unit that calculates a likelihood value and extracts a first arrival angle candidate of an arrival wave in the first direction that includes at least the first maximum likelihood value;
The reception signal of the second virtual linear array, which is formed of virtual reception antennas linearly arranged in a second direction orthogonal to the first direction, among the plurality of virtual reception antennas, A second maximum likelihood value corresponding to the NW angles in the second direction is calculated by maximum likelihood estimation processing for two directions, and an arrival in the second direction including at least the second maximum likelihood value is calculated. A second estimation unit that extracts a second arrival angle candidate of the wave;
Thirdly, using the first arrival angle candidate and the second arrival angle candidate, the third embodiment estimates an arrival angle of the NW arrival waves in a two-dimensional plane extending in the first direction and the second direction. Estimation part of,
Radar equipment. The third estimation unit is configured to select the two-dimensional plane from among combinations of the NW angles corresponding to the first maximum likelihood value and the NW angles corresponding to the second maximum likelihood value. Determine the angle of arrival of the NW arriving waves at
The radar apparatus according to claim 1. The first estimation unit determines the NW angles corresponding to the first maximum likelihood value, and the first maximum likelihood value in a first evaluation function used in the maximum likelihood estimation process. Extracting the first arrival angle candidate including the NW angles corresponding to at least one extremum;
The second estimation unit determines the NW angles corresponding to the second maximum likelihood value, and the second maximum likelihood value in a second evaluation function used in the maximum likelihood estimation process. Extracting the second arrival angle candidate including the NW angles corresponding to at least one extremum;
The third estimation unit determines the arrival angles of the NW arrival waves in the two-dimensional plane from among the combination of the first arrival angle candidate and the second arrival angle candidate.
The radar apparatus according to claim 1. The third estimation unit performs maximum likelihood estimation processing on the two-dimensional plane with respect to a combination of the first arrival angle candidate and the second arrival angle candidate to obtain the NW number of the NW in the two-dimensional plane. Estimate the angle of arrival of the incoming wave,
The radar apparatus according to claim 1. The third estimation unit estimates the arrival angles of the NW arrival waves in the two-dimensional plane by the steepest gradient method using the first arrival angle candidate and the second arrival angle candidate as initial values. Do,
The radar apparatus according to claim 1. In the maximum likelihood estimation process, an evaluation function including a reception signal of the virtual reception antenna and a direction vector of the virtual reception antenna is used.
Among the parameters used for the evaluation function, parameters related to the direction vector are stored in advance.
The radar apparatus according to claim 1. A direction-of-arrival estimation apparatus for estimating an angle of arrival of a received signal using a plurality of receiving antennas, comprising:
The maximum likelihood estimation process for the first direction is performed using a reception signal of a first linear array constituted by the reception antennas arranged in the first direction among the plurality of reception antennas. Calculating a first maximum likelihood value corresponding to NW (NW is an integer of 1 or more) angles in one direction, and at least the first of the incoming wave in the first direction including the first maximum likelihood value; A first estimation unit that extracts an arrival angle candidate of
The second direction using the reception signal of the second linear array configured by the reception antennas linearly arranged in the second direction orthogonal to the first direction among the plurality of reception antennas. Calculating a second maximum likelihood value corresponding to the NW angles in the second direction by the maximum likelihood estimation process for the second direction, the second maximum likelihood value of the arrival wave in the second direction including at least the second maximum likelihood value A second estimation unit that extracts two arrival angle candidates;
Thirdly, using the first arrival angle candidate and the second arrival angle candidate, the third embodiment estimates an arrival angle of the NW arrival waves in a two-dimensional plane extending in the first direction and the second direction. And an estimation unit of
Direction of arrival estimation device.

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